MCP Server for YNAB

Turn natural-language budget questions into safe, local YNAB API workflows
Give your AI assistant read-only budget access by default, with explicit write opt-in

67 tools + 4 discovery helpers • 6 guided prompts • undo journal • 45 read-only operations by default • read-only by default

Quick Start • Plugin • Claude Code • Codex • Other Hosts • What You Can Do • Tools Reference • Configuration

Run YNAB through Claude Code, Codex, Hermes, Antigravity, or any stdio MCP host. For clients that need a remote URL, the hosted connector at https://ames-ynab.link/mcp signs each user in through YNAB OAuth, with no personal access token to copy into another service. Both paths use the same rate-aware tool layer and convert amounts between dollars and YNAB milliunits. Direct registration starts read-only, and the undo journal records supported changes. Some operations still require manual recovery in YNAB.

Why This Exists

YNAB's budgeting philosophy works best when you interact with your budget frequently, but the app interface is not designed for quick questions or careful bulk cleanup. "How much did I spend on groceries this month?" should not require navigating three screens. "Categorize all my Amazon orders from this week" should not become a manual, one-by-one review.

This server gives your AI assistant a local interface to YNAB's API, turning natural language into structured budget review and, when explicitly enabled, budget operations. It is designed for real budgeting work: finding overspending, reviewing unapproved transactions, checking category drift, investigating recurring payments, and making verified batch updates without giving the assistant broader access than it needs.

All monetary values are automatically converted between dollars and YNAB's internal milliunits format so the AI never has to think about it. The server uses the official YNAB JavaScript SDK where it fits, plus direct API calls for newer endpoints and query parameters that the SDK has not caught up with yet.

Quick Start

Requires Node.js 20 or later for local use. Add this to an MCP client that supports stdio servers:

{
  "mcpServers": {
    "ynab": {
      "command": "npx",
      "args": ["-y", "@oliverames/mcp-server-for-ynab@latest"],
      "env": {
        "YNAB_OP_PATH": "op://Development/YNAB/credential"
      }
    }
  }
}

This example uses the 1Password CLI. Replace the reference with your own item, or inject YNAB_API_TOKEN through your launcher. Ask for ynab_auth_status first to inspect credential status without a YNAB API call.

This package stands on its own as a stdio MCP server. You can register the npm package directly and let your MCP client launch it on demand. Plugin packages are also provided for separately managed Claude Code and Codex marketplaces, plus the included Hermes and Antigravity catalogs. You do not need the older ames-connectors marketplace for YNAB.

The npm package is the local, owner-run option. It uses a personal access token because the account owner runs the process. The same repository also powers a hosted OAuth connector for clients that accept remote MCP URLs.

Connect to the hosted remote server

Add this Streamable HTTP URL to Claude.ai, ChatGPT, Mistral Vibe Work, or another remote MCP client:

https://ames-ynab.link/mcp

The old https://ynab.amesvt.com/mcp endpoint has been retired. If a client still uses the old hostname, add the new URL as a new connection and authorize there; OAuth tokens stay bound to the hostname where they were issued. Stored credentials and journals are preserved, but a new consent has its own isolated journal. See the migration and rollback plan.

The client opens this connector's consent page and then sends you to YNAB to sign in. Leave the write-access box unchecked for a read-only connection, or enable it when you need the write tools. The connector stores OAuth tokens and undo data with application-layer encryption in Cloudflare KV; the AI client receives only the connector's own scoped token. See the live privacy policy, data-deletion flow, and deployment documentation.

The July 15 acceptance record documents earlier signed-in checks. It isn't a current availability check. The Worker supports scoped authorization, encrypted token storage, and account deletion. High-impact tools retain their confirmed: true input requirement after write access is enabled.

Install as a Plugin

Claude and Codex plugin packages remain available for distribution through a separately managed marketplace. This repository no longer supplies their root catalogs. For direct use, register the npm package with your MCP client.

The plugin starts @oliverames/mcp-server-for-ynab@latest and preserves the prior ames-ynab connector behavior by setting YNAB_ALLOW_WRITES=1. Direct MCP registration remains read-only unless you explicitly enable writes.

Other Plugin Hosts

The repository also carries host-specific marketplace and plugin manifests for Hermes and Antigravity:

Host	Marketplace	Plugin manifest	MCP config
Claude Code	Separately managed	`.claude-plugin/plugin.json`	`.mcp.json`
Codex	Separately managed	`codex/.codex-plugin/plugin.json`	`codex/.codex-plugin/mcp.json`
Hermes	`.hermes-plugin/marketplace.json`	`.hermes-plugin/plugin.json`	`.hermes-plugin/mcp.json`
Antigravity	`.antigravity-plugin/marketplace.json`	`.antigravity-plugin/plugin.json`	`.antigravity-plugin/mcp_config.json`

1. Get a YNAB Personal Access Token

Go to YNAB Developer Settings and create a new personal access token.

Do not ask another YNAB user for a personal access token. If you are building a public connector for accounts you do not own, use YNAB OAuth instead.

Credential lookup order:

Values passed directly to the MCP process, such as YNAB_API_TOKEN.
The detected host's plaintext settings: Codex reads ~/.codex/config.toml, first [shell_environment_policy.set], then [mcp_servers.ynab.env]; Claude Code reads ~/.claude/settings.json under top-level env.
The other supported agent config as a fallback, useful when a token is already stored locally but the launcher did not inject it.
YNAB_API_TOKEN_FILE, if configured in any of the sources above.
YNAB_OP_PATH, if configured in any of the sources above and the op CLI is available.

If no token is found, ynab_auth_status returns a structured setup guide. Agents should first ask whether the user already has the YNAB token in a password manager such as 1Password. If yes, ask permission before configuring YNAB_OP_PATH; otherwise ask the user to add YNAB_API_TOKEN to the correct Codex or Claude config file and restart the MCP server.

2. Install in Claude Code

Use user scope if you want the server available in all Claude Code projects:

claude mcp add ynab --scope user \
  -e YNAB_API_TOKEN=your-token-here \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

Add a default budget ID if you do not want tools to use YNAB's last-used budget:

claude mcp add ynab --scope user \
  -e YNAB_API_TOKEN=your-token-here \
  -e YNAB_BUDGET_ID=optional-default-budget-id \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

Use --scope project instead of --scope user if you want Claude Code to write a project-local .mcp.json.

If ~/.claude/settings.json already contains env.YNAB_API_TOKEN, you may omit -e YNAB_API_TOKEN=...; the server will read the Claude setting as a fallback if the launcher does not inject it.

Verify Claude Code can see the server:

claude mcp get ynab

If Claude Code reports that ynab already exists, remove the old entry and run the add command again:

claude mcp remove ynab

3. Install in Codex

Register the same npm package directly with Codex:

codex mcp add ynab \
  --env YNAB_API_TOKEN=your-token-here \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

With a default budget ID:

codex mcp add ynab \
  --env YNAB_API_TOKEN=your-token-here \
  --env YNAB_BUDGET_ID=optional-default-budget-id \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

If ~/.codex/config.toml already contains YNAB_API_TOKEN under [shell_environment_policy.set] or [mcp_servers.ynab.env], you may omit --env YNAB_API_TOKEN=...; the server will read the Codex setting as a fallback if the launcher does not inject it.

Verify Codex can see the server:

codex mcp get ynab

If Codex reports that ynab already exists, remove the old entry and run the add command again:

codex mcp remove ynab

4. Enable Write Tools (Optional)

By default, the server registers read-only tools only. To expose tools that create, update, import, or delete YNAB data, add YNAB_ALLOW_WRITES=1 when you register the server:

claude mcp add ynab --scope user \
  -e YNAB_API_TOKEN=your-token-here \
  -e YNAB_ALLOW_WRITES=1 \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

codex mcp add ynab \
  --env YNAB_API_TOKEN=your-token-here \
  --env YNAB_ALLOW_WRITES=1 \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

Every write requires an exact preview from preview_write_tool, its session-bound single-use previewToken, and confirmed: true after explicit human approval of the plan. A token is not human consent. Execution rereads fresh state and rejects changed IDs, budget or values; expectedMatchedCount is an additional check, never a replacement. Pending bank imports cannot be previewed exactly; initiate them in YNAB and review the imported rows here.

Manual JSON Config

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "ynab": {
      "command": "npx",
      "args": ["-y", "@oliverames/mcp-server-for-ynab"],
      "env": {
        "YNAB_API_TOKEN": "your-token-here"
      }
    }
  }
}

Generic MCP client:

{
  "mcpServers": {
    "ynab": {
      "command": "npx",
      "args": ["-y", "@oliverames/mcp-server-for-ynab"],
      "env": {
        "YNAB_API_TOKEN": "your-token-here"
      }
    }
  }
}

If you prefer a global install, point your MCP client at the package binary directly:

npm install -g @oliverames/mcp-server-for-ynab

{
  "mcpServers": {
    "ynab": {
      "command": "mcp-server-for-ynab",
      "env": {
        "YNAB_API_TOKEN": "your-token-here",
        "YNAB_BUDGET_ID": "optional-default-budget-id"
      }
    }
  }
}

Docker (Optional)

The repository ships a Dockerfile (also used by registry-hosted builds such as Glama). The container speaks MCP over stdio:

docker build -t mcp-server-for-ynab .
docker run -i --rm -e YNAB_API_TOKEN=your-token-here mcp-server-for-ynab

Add -e YNAB_ALLOW_WRITES=1 to enable write tools, and -e YNAB_BUDGET_ID=... for a default budget.

1Password Token Lookup (Optional)

If your token is stored in 1Password, set YNAB_OP_PATH instead of YNAB_API_TOKEN. The op CLI must be installed and authenticated in the environment that launches the MCP server.

claude mcp add ynab --scope user \
  -e YNAB_OP_PATH="op://Personal/YNAB API Token/credential" \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

codex mcp add ynab \
  --env 'YNAB_OP_PATH=op://Personal/YNAB API Token/credential' \
  -- npx -y @oliverames/mcp-server-for-ynab@latest

Local Smoke Test

From this repo, you can verify the published npm package without changing any MCP client config:

YNAB_API_TOKEN=your-token-here npm run smoke:review-unapproved -- --published

What You Can Do

Ask your AI...	What happens under the hood
"How much did I spend on groceries this month?"	`search_categories` → `get_month_category`
"Show me all unapproved transactions"	`review_unapproved` groups by readiness
"Log a $50 Costco trip under groceries"	`search_payees` → `search_categories` → `create_transaction`
"Record my $250 Visa payment from checking"	`create_transaction` with `transferToAccountName: "Visa"` (the server resolves the transfer payee)
"Find the $12.34 charge from last week"	`search_transactions` with `amount: 12.34` (or `query: "onion river"`)
"Set up monthly $1,500 rent on the 1st"	`create_scheduled_transaction` with `monthly` frequency
"Move $200 from emergency fund to dining"	`search_categories` → `update_month_category` (x2)
"Categorize all my Amazon orders from this week"	`get_transactions` (filtered) → `update_transactions` (batch)
"Create a 'Side Projects' spending category"	`search_categories` (find group) → `create_category`
"How has my budget been re-allocated this month?"	`get_money_movements_by_month`
"What subscriptions am I actually paying for?"	`detect_recurring_charges` finds payee + amount + cadence patterns with annual cost
"How am I doing financially?"	`get_budget_health` scores savings rate, age of money, and overspending green/yellow/red
"Are my credit card payments fully funded?"	`audit_credit_card_payments` compares card balances to payment categories
"Merge my duplicate coffee categories"	`merge_category` moves transactions and budgets in one confirmed call
"Split that Costco charge across three categories"	`prepare_split_for_matching` mirrors the imported transaction for UI matching
"Undo that last batch approval"	`list_undo_history` → `undo_operation` restores the journaled before-state
"Import my latest bank transactions"	`import_transactions` triggers linked account sync

Features

The source defines 67 tools for the YNAB v1 REST API and four discovery helpers, for 71 registered MCP operations. Read-only mode exposes 42 YNAB operations and three helpers. Enabling writes adds 25 YNAB operations and the write-execution helper. The server also defines MCP prompts and resources:

Resource	Tools	Capabilities
Budgets	4	List, view details, settings
Accounts	3	List, view, create
Categories	9	Create and update categories/groups, search, goals, monthly budgets
Payees	5	List, view, create, rename, search
Payee Locations	3	GPS coordinates for mobile transactions
Months	2	Monthly summaries with per-category breakdown
Money Movements	4	Budget re-allocation tracking
Transactions	12	Create, read, update, delete, bulk operations, matching, and filters
Scheduled Transactions	5	Full CRUD for recurring transactions
Convenience	2	Unapproved transaction review and overspending checks
Workflows	3	Category merge/retire, split-via-match for imported transactions
Audits	2	Credit card payment funding, reconciliation diagnosis
Analytics	3	Budget health, income/expense + savings rate, recurring-charge detection
Undo & Export	3	Local undo history, supported reversal, CSV export
Tool Discovery	4	Authentication status, tool index, read and write executors

Beyond tools, the server ships 6 MCP prompts (guided workflows: monthly review, weekly triage, categorize-and-approve, subscription audit, reconciliation, credit card audit) and 4 MCP resources (ynab://guide/*: YNAB methodology, write-safety rules, audit patterns, review flags reference).

Design Decisions

Read-only by default - write tools are not registered unless YNAB_ALLOW_WRITES=1 is set. Read tools are annotated with readOnlyHint: true; write tools are annotated with readOnlyHint: false, idempotency hints, and destructive hints for delete operations.
Server instructions and structured contracts - the server sends a compact instructions block at initialize (dollar amounts, search_transactions before unfiltered pulls, transactionId, the transfer convenience, write-safety rules), so clients that never open a prompt or resource still get the rules that matter. Every tool exposes a human-readable title, an input schema even when it takes no arguments, a minimal output schema, and matching structuredContent. Impact hints describe YNAB as a private, bounded system so app clients can distinguish reads, writes, and destructive operations accurately.
Exact write previews and confirmation - every write requires a session-bound single-use preview token and confirmed: true after explicit user approval. Bulk-filter writes also support expectedMatchedCount as an additional guard.
Dollar amounts everywhere - inputs and outputs are in dollars (-12.34), never milliunits (-12340). Conversion is automatic and transparent.
Smart budget resolution - set YNAB_BUDGET_ID for a default, or omit it to auto-resolve to your last-used budget. Every tool accepts an optional budgetId override.
Pinned YNAB host - all HTTP requests are restricted to https://api.ynab.com, redirects are not followed, and API tokens are redacted from surfaced errors.
Agent-aware token fallback - use direct process env, Codex ~/.codex/config.toml, Claude ~/.claude/settings.json, a small token file via YNAB_API_TOKEN_FILE, or a 1Password CLI reference via YNAB_OP_PATH.
Split transactions - first-class support for subtransactions in create, read, and format operations. Updates can also convert a non-split transaction into a split (the YNAB API does not support editing the subtransactions of an existing split).
Current transaction filters - transaction list tools support sinceDate, untilDate, type filters, resource filters, and delta requests. YNAB defaults omitted sinceDate to one year ago, so pass an explicit older date when you need older history.
Bulk operations - create_transactions and update_transactions handle arrays in a single API call. Bulk updates can look transactions up by id or by importId.
Verified batch updates - update_transactions refetches the whole batch in a single list request after the bulk API call, reports mismatched fields without retrying financial writes, and returns a verification block so approval counts cannot hide failed category writes. Journal entries reuse the verified after-state.
Fetch-then-merge updates - scheduled transaction updates (which use PUT semantics) automatically fetch the current state and merge your changes, so you only specify what changed.
Transfer convenience - create_transaction and create_transactions accept transferToAccountId or transferToAccountName and resolve the destination account's transfer_payee_id themselves, so a credit card payment is one call with no payee lookup. YNAB's own error for a Transfer -- … payee name now carries the same pointer.
Fuzzy search - search_categories and search_payees do case-insensitive partial matching across all entries, and search_transactions does the same over transactions (payee, raw import string, memo, account, category, split rows) with an optional absolute-amount match and limit / offset paging. Category search covers both the category name and its group name, tokenizes multi-word queries and OR-matches them (so gym fitness membership still lands), ranks whole-phrase and name hits above single-token and group-only hits, and reports matched_on / matched_terms per result. It does no synonym expansion, an empty result says so and points at list_categories.
Decoded text - YNAB stores some strings HTML-escaped (bank imports are the usual source). Names, memos and notes are entity-decoded on the way out, so a payee reads as B&H Photo Video rather than B&H Photo Video, and name search matches either spelling. Writes send exactly what the caller supplied.
Approval workflow with anomaly flags - review_unapproved scans the full transaction history for unapproved entries (YNAB's API defaults to the last year, which would silently hide older stragglers) and groups transactions into "ready to approve" (categorized, split, or transfer) and "needs attention" (uncategorized), and attaches a flags array to each transaction surfacing anomalies: manually_entered (not bank-imported), match_broken (stale match reference), scheduled_transaction_realized, new_payee, no_prior_amount_match (novel amount for this payee), and category_drift:was_X (payee categorized differently in the prior 60 days). Group-level flags aggregate the union of all transaction flags. Bulk approval requires confirmed: true.
Honest group headers - a by_payee group describes all of its rows, not just the first one. Groups carry category_names (every distinct category in the group) plus mixed_categories, and category_name is null whenever the group spans more than one category. total is the net; a group whose rows run both directions also carries mixed_amount_signs: true with inflow_total and outflow_total, so a net that nets refunds against charges cannot be read as a single small charge.
Nullable updates - update tools accept null for clearable fields (memo, payeeName, categoryId, flagColor) to distinguish "don't change" (omit) from "clear this field" (null).
Target behavior support - category create/update tools expose goalNeedsWholeAmount for YNAB's "Set aside another" vs. "Refill up to" goal behavior.
Delta request support - high-volume list tools accept lastKnowledgeOfServer and return server_knowledge when that parameter is provided. get_budget supports full delta exports: pass lastKnowledgeOfServer to receive every entity changed since that knowledge in one response.
Undo journal - every transaction write is journaled locally with before-state (~/.ynab-mcp-undo.json); list_undo_history reviews it and undo_operation reverses a journaled write. Category/payee/scheduled writes are journaled for audit without automatic undo.
Prompts and resources - guided workflow prompts (monthly review, weekly triage, categorize-and-approve, subscription audit, reconciliation, credit card audit) and a general YNAB-methodology knowledge base as MCP resources, so any host gets the working discipline without a separate skill.
Rate-budget surfacing - responses warn the model when 50 or fewer requests remain in the trailing hour, on top of the client-side limiter that enforces the budget.
Debt account support - loan and debt accounts include debt_original_balance, debt_interest_rates, debt_minimum_payments, and debt_escrow_amounts with correct unit conversion (rates stay as percentages, payments convert from milliunits).

Tools Reference

Read tools are available by default. Tools that create, update, import, or delete YNAB data are marked as write tools and are registered only when YNAB_ALLOW_WRITES=1.

User & Budgets

Tool	Description
`get_user`	Get the authenticated user
`list_budgets`	List all budgets with IDs, names, date ranges, format settings, and default budget. Pass `includeAccounts: true` to include each budget's accounts.
`get_budget`	Get budget summary (name, currency, account/category/payee counts). Pass `lastKnowledgeOfServer` for a delta export of every changed entity plus the next `server_knowledge`.
`get_budget_settings`	Get currency and date format settings

Accounts

Tool	Description
`list_accounts`	List all accounts with balances, debt details, and import status
`get_account`	Get full account details including notes and debt fields
`create_account`	Write tool: create a new account (checking, savings, creditCard, mortgage, etc.)

Supported account types: checking, savings, cash, creditCard, lineOfCredit, otherAsset, otherLiability, mortgage, autoLoan, studentLoan, personalLoan, medicalDebt, otherDebt

Categories & Category Groups

Tool	Description
`list_categories`	List all category groups and their categories with budgeted/activity/balance. Groups and categories carry `hidden`, `deleted`, and `internal` flags (`internal` marks YNAB's own categories such as Credit Card Payments).
`get_category`	Get full category details including goal progress and cadence
`get_month_category`	Get category budget for a specific month
`update_month_category`	Write tool: set the budgeted amount for a category in a month
`update_category`	Write tool: update name, note, goal target, goal target date, or move to a different group. `goalFrequency` (`monthly` / `weekly` / `yearly`, YNAB API 1.86) sets a recurring target; it requires `goalTarget` and cannot be combined with `goalTargetDate`.
`create_category`	Write tool: create a new category in an existing group, with an optional goal including a recurring `goalFrequency` target
`create_category_group`	Write tool: create a new category group
`update_category_group`	Write tool: rename a category group
`search_categories`	Case-insensitive partial name search over category names and category-group names (e.g., "groc" finds "Groceries"; "health" finds everything in a "Health & Medical" group). Multi-word queries are tokenized and OR-matched, results are ranked, and each result reports `matched_on` / `matched_terms`. Pass `includeHidden: true` to search hidden categories and groups.

Payees

Tool	Description
`list_payees`	List all payees with transfer account mappings
`get_payee`	Get payee details
`create_payee`	Write tool: create a new payee
`update_payee`	Write tool: rename a payee
`search_payees`	Case-insensitive partial name search

Payee Locations

Tool	Description
`list_payee_locations`	List all payee locations (GPS coordinates from mobile app)
`get_payee_location`	Get a specific payee location
`get_payee_locations_by_payee`	Get all locations for a specific payee

Months

Tool	Description
`list_months`	List budget months with income, budgeted, activity, to-be-budgeted, age of money, and notes
`get_month`	Get month detail with per-category budget/activity/balance/goal breakdown

Money Movements

Tool	Description
`list_money_movements`	List all money movements (budget re-allocations between categories)
`get_money_movements_by_month`	Get money movements for a specific month
`list_money_movement_groups`	List all money movement groups (batched re-allocations)
`get_money_movement_groups_by_month`	Get money movement groups for a specific month

Transactions

Tool	Description
`get_transactions`	Get transactions with filters: by account, category, payee, month, status (`unapproved`/`uncategorized`), `sinceDate`, and `untilDate`. Non-delta results stop at 500 rows by default (`limit` up to 2000, page with `offset`); a capped or paged result returns `{ transactions, total, returned, offset, has_more, next_offset }` instead of a bare array. Prefer `search_transactions` when you are looking for specific rows.
`search_transactions`	Server-side search with pagination: `query` is a case-insensitive substring match over payee name, raw bank import string, memo, account, category, and split rows; `amount` matches on absolute value (12.34 finds a -12.34 outflow). Optional `accountId` / `sinceDate` / `untilDate` bound the scan; `limit` (default 50) and `offset` page through `total_matches`, newest first, with `next_offset` for the following page.
`get_transaction`	Get a single transaction by ID. The argument is `transactionId`, not `id` (includes subtransactions). Auto-handles composite scheduled-transaction IDs like `uuid_YYYY-MM-DD`; if the underlying matched transaction has been deleted, falls back to returning the active scheduled template wrapped as `{ resource_type: "scheduled_transaction", ... }`.
`create_transaction`	Write tool: create a transaction with optional split (subtransactions must sum to total). For a transfer (including a credit card payment) pass `transferToAccountId` or `transferToAccountName` instead of a payee; the server resolves the destination account's internal transfer payee, since YNAB rejects a literal `Transfer -- …` payee name.
`create_transactions`	Write tool: bulk create multiple transactions in a single API call (supports split transactions and the same `transferToAccountId` / `transferToAccountName` convenience per entry)
`update_transaction`	Write tool: partial update - only specified fields change. Can convert a non-split transaction into a split via `subtransactions`. Composite scheduled-transaction IDs (`uuid_YYYY-MM-DD`) are writable, see below.
`update_transactions`	Write tool: batch update multiple transactions at once (look up each entry by `id` or `importId`), then verify requested fields persisted using a single batch refetch. Returns `newly_approved_count` beside `approved_count`. Pass `returnSummary: true` for compact counts instead of full objects on large batches (avoids overflowing the tool-result size limit).
`approve_transactions`	Write tool: approve unapproved transactions in bulk by filter (`payeeId` / `categoryId` / `accountId`) without hand-listing IDs. Skips uncategorized transactions by default, requires `confirmed: true`, and supports `expectedMatchedCount`.
`reassign_payee_transactions`	Write tool: move all transactions from one payee to another, the merge workaround since the YNAB API has no payee delete/merge endpoint. Requires `confirmed: true` and supports `expectedMatchedCount`.
`delete_transaction`	Write tool: delete a transaction. Requires `confirmed: true`.
`import_transactions`	Write tool: trigger import from linked bank accounts

Scheduled Transactions

Tool	Description
`list_scheduled_transactions`	List all recurring transactions
`get_scheduled_transaction`	Get a specific scheduled transaction
`create_scheduled_transaction`	Write tool: create a recurring transaction with frequency
`update_scheduled_transaction`	Write tool: update (fetch-then-merge preserves unchanged fields)
`delete_scheduled_transaction`	Write tool: delete a scheduled transaction. Requires `confirmed: true`.

Supported frequencies: never, daily, weekly, everyOtherWeek, twiceAMonth, every4Weeks, monthly, everyOtherMonth, every3Months, every4Months, twiceAYear, yearly, everyOtherYear

Convenience

Tool	Description
`preview_write_tool`	Read fresh before-state and exact proposed write intent; returns a five-minute single-use session-bound token. Separate user approval is required.
`suggest_transaction_categories`	Read-only payee-history/recency/schedule suggestions with confidence/evidence and uncertainty/split abstention; never auto-applies.
`review_unapproved`	Get unapproved transactions grouped by readiness: "ready to approve" (categorized, split, or transfer) vs. "needs category first" (uncategorized). Each transaction includes a `flags` array highlighting anomalies (manually_entered, match_broken, no_prior_amount_match, category_drift, new_payee, scheduled_transaction_realized) computed against 60 days of payee history. Group headers report `category_names` / `mixed_categories` and, when the rows run both directions, `inflow_total` / `outflow_total` beside the net `total`. Includes a warning against blind approval. Pass `summary: true` for counts + by-payee aggregates only, or `compact: true` to keep per-transaction rows (with IDs) while dropping bulky fields so the response fits inline, `match_broken` rows keep `matched_transaction_id` in compact mode, since triaging that flag means looking the matched id up. Above `maxTransactions` unapproved rows (default 400) a full response degrades to `compact`, and above twice that to `summary`; the response reports `mode` and a `notice`.
`get_overspent_categories`	Get categories with negative balances for a month, useful for finding prior-month overspending that reduces the current month's Ready to Assign.

Workflows (v4.0)

The YNAB API has no category merge/delete endpoint and cannot split an already-imported transaction; these composite tools do everything the API allows and report the remaining manual UI step.

Tool	Description
`move_category_budget` (write)	Durable exact-value category allocation move for one month, with fresh readback and explicit recovery.
`list_operations`	Tenant-isolated durable partial/unknown/completed workflow state; filter by budget or inspect all authorized journal budgets.
`resume_operation` (write)	Recover verified pending steps after a new preview and explicit approval; conflicts stop safely.
`merge_category` (write)	Recategorize every transaction from one category into another and move budgeted amounts (`moveBudgetedMonths: none/current/all`, capped at 24 months). The emptied source category is then hidden/deleted by hand in the YNAB UI. Requires `confirmed: true`.
`retire_category` (write)	Prepare a category for deletion: move its transaction history to a replacement category and zero its budgets (dollars return to Ready to Assign). Requires `confirmed: true`.
`prepare_split_for_matching` (write)	Create a mirror unapproved split transaction that YNAB will offer to match with an imported original, the only way to get splits onto a bank-imported transaction. Requires `confirmed: true`.

Audits & Analytics (v4.0, read-only)

Tool	Description
`audit_credit_card_payments`	Compare each credit card's balance against its Credit Card Payment category and report underfunded cards.
`audit_account_reconciliation`	Per-account reconciliation status; with `accountId`, lists the exact uncleared/unapproved items to check against the bank statement.
`get_budget_health`	Snapshot with green/yellow/red indicators: savings rate, age of money, Ready to Assign, overspending, credit card debt.
`get_income_expense_summary`	Net income/spending and savings, with refunds/reversals, localized category identities and split/transfer accounting. Ambiguous metadata requires explicit income category IDs.
`get_spending_trends`	Net category/payee monthly trends and carefully labeled unusual-spending observations with threshold evidence.
`forecast_scheduled_balances`	Future scheduled-payment account ledger scenarios, including transfer effects and explicit omissions.
`detect_recurring_charges`	Find subscriptions/recurring charges from history by payee + amount + cadence, with estimated annual cost.
`export_transactions`	Export filtered transactions as CSV text. Capped at `maxRows` (default 500, max 2000); when exceeded the newest rows are kept and a second text block reports the truncation.

Undo Journal (v4.0)

Transaction writes retain relevant before/verified-after state in ~/.ynab-mcp-undo.json when storage is available. Up to 100 recent completed/audit entries are retained; unfinished durable category operations are preserved. The file contains sensitive plaintext financial fields, uses mode-600 permissions and atomic locked replacement, and survives restarts. Hosted journals are encrypted per OAuth consent. Undo history is tenant-isolated; legacy unverified entries cannot be restored automatically.

Tool	Description
`list_undo_history`	List journaled writes, newest first, with undo capability per entry. Reads only the local journal.
`undo_operation` (write)	Reverse a journaled write: restore updated fields, delete created transactions, or recreate a deleted one (without its original bank-import linkage). One undo per entry. Requires `confirmed: true`.

Resolve broken match references

Pass matched_transaction_id values from review_unapproved (including compact rows) to resolve_matched_transactions as matchedTransactionIds, with an optional budgetId. Each batch accepts 1–50 IDs and fetches each distinct ID once. It checks budget access first. Results contain the original matched ID and either orphan for a transaction 404 or found with the formatted transaction in dollars. Found rows require duplicate review before any separate write. Authentication, rate-limit, network, and other failures return an error, not orphan results. The tool performs only reads and never changes match links.

Workflow Safety Notes

Write Tool Opt-In

The server starts in read-only mode. Write tools are not merely discouraged; they are absent from listTools unless YNAB_ALLOW_WRITES=1 is present when the MCP process starts. This mirrors the safer hosted-connector pattern: the default permission set can inspect budgets, transactions, categories, payees, months, and scheduled transactions, but it cannot mutate financial data.

If a client already has the process running, changing the environment is not enough. Restart the MCP server after setting or clearing YNAB_ALLOW_WRITES.

Call the read-only preview_write_tool with a concrete write tool and its input:

{
  "tool_name": "update_transactions",
  "input": {
    "budgetId": "budget-id",
    "transactions": [{ "id": "transaction-id", "categoryId": "category-id" }]
  }
}

Present the returned before-values and proposed changes to the user. After explicit approval, call that tool with the same input plus previewToken from preview_token and confirmed: true. Tokens expire after five minutes and are consumed on an attempted execution, including stale-state rejection. They cannot move between sessions, budgets, transaction IDs or requested values. Bank memos and merchant strings are untrusted data and cannot authorize edits.

The server reads fresh state again and restricts outbound mutations to the approved exact intent. A changed match count or changed values at the same count require a new preview and approval. YNAB has no conditional writes: an external change can still race the final read and write.

move_category_budget, merge_category and retire_category persist their exact steps before writing and read back every step. Use list_operations and a newly approved resume_operation after a partial or unknown result; never blindly repeat a financial operation. Unverified or conflicting undo is refused, and an uncertain non-idempotent recreation undo is blocked from replay until manual reconciliation. See recovery limits.

Read freshness and projections

Transaction, account, category, payee and schedule lists accept projection: "lean" | "full", freshness: "fresh" | "cached" and includeFreshness. Fresh is the default. Explicit caching uses tenant/session/budget-isolated merged entities and a 30-second TTL. Transaction metadata reports the exact history_since boundary; an older requested date expands the baseline, and complete applies to the reported coverage. Caller deltas never seed the merged baseline. Writes invalidate the cache even after response loss. See read-cache details.

Batch Updates

When a batch operation categorizes and approves transactions at the same time, do not use review_unapproved counts as the only success check. Approved transactions leave the review queue even if a category write failed, so queue counts can hide approved-but-still-uncategorized transactions.

update_transactions protects this path by refetching the batch after the bulk API call (one list request for the whole batch, not one request per transaction) and comparing the persisted fields with the requested fields. If anything differs, it reports the conflict or unapplied fields without replaying financial writes. Split verification checks every active line, including requested amount/category/payee/memo; generated line IDs and response order do not affect equality. The response includes:

{
  "verification": {
    "checked": 1,
    "retried": [],
    "failed": []
  }
}

Treat any failed entry as a real write failure and inspect the named transaction with get_transaction.

Approval counts

Batch responses report two different approval numbers, and only one of them answers "what did this call approve?":

{
  "updated_count": 9,
  "approved_count": 3,
  "newly_approved_count": 1,
  "already_approved_count": 2,
  "approval_state_unknown_count": 0
}

approved_count is how many rows in the batch are approved now, including rows that were already approved when the batch was submitted. newly_approved_count is how many rows this call actually flipped, measured against the pre-write fetch; already_approved_count and approval_state_unknown_count (no before-state available, e.g. an importId row whose refetch failed) account for the rest. Report newly_approved_count to a user. approve_transactions only ever touches rows that were unapproved when it fetched them, so there the two are equal.

Composite Scheduled-Transaction IDs

A scheduled transaction that has realized carries a composite ID of the form d9e7c3c2-…_2026-07-30 (the shape review_unapproved flags as scheduled_transaction_realized). The suffix makes the ID look synthetic, and the natural assumption is that such a row is read-only or that the suffix must be stripped before writing. Neither is true: pass the ID exactly as returned and update_transaction / update_transactions apply memo, category and approval to the realized transaction, returning the full updated object. Reads are equally forgiving, get_transaction strips the suffix itself and falls back to the scheduled template when the underlying matched transaction has been deleted.

Credit Card Payment Transfers

If two unapproved transactions are clearly a credit card payment plus the matching checking-account outflow, convert them into a transfer before approval. Approving both sides as ordinary categorized transactions preserves the wrong structure and creates cleanup work.

Manual YNAB transfer fixes can replace one side of the pair with a new transaction ID. Read-only verification should not assume both original IDs survive. If one old ID returns resource_not_found, inspect recent activity in both involved accounts and verify the pair by transfer_transaction_id cross-links.

Environment Variables

Variable	Required	Default	Description
`YNAB_API_TOKEN`	Yes*	(none)	Personal access token from YNAB Developer Settings. Read from process env first, then supported Codex and Claude plaintext agent settings.
`YNAB_API_TOKEN_FILE`	No	(none)	Path to a file containing only the token. The file must be 4 KB or smaller. Used only when `YNAB_API_TOKEN` is unset, and can be provided through process env or agent settings.
`YNAB_BUDGET_ID`	No	`last-used`	Default budget ID. If omitted, tools use YNAB's most recently accessed budget. Run `list_budgets` to find IDs.
`YNAB_ALLOW_WRITES`	No	read-only	Set to `1` to register write tools. Any other value keeps the server read-only.
`YNAB_OP_PATH`	No	(none)	1Password secret reference for your API token. Used only if no direct token is configured. Can be provided through process env or agent settings.
`YNAB_DISABLE_AGENT_CONFIG_FALLBACK`	No	`0`	Set to `1` to stop the server from reading `~/.codex/config.toml` and `~/.claude/settings.json`. Intended for tests and tightly controlled runtimes.
`YNAB_RATE_LIMIT_PER_HOUR`	No	`190`	Client-side rate limiter. Set to `0` to disable for controlled tests.
`YNAB_RATE_LIMIT_BURST`	No	`10`	Maximum burst size before rate limiting pauses requests.
`YNAB_HTTP_TIMEOUT_MS`	No	`30000`	Per-request timeout in milliseconds. Set to `0` to disable the timeout.
`YNAB_HTTP_RETRIES`	No	`2`	Automatic retries for retryable failures. HTTP 429 (rate limited) retries any request because YNAB rejected it before processing; 502/503/504 and network errors retry reads (`GET`/`HEAD`) only. Honors `Retry-After`. Set to `0` to disable.
`YNAB_MAX_RESPONSE_BYTES`	No	`8388608`	Maximum direct-fetch response size for newer endpoints.

*YNAB_API_TOKEN is required unless YNAB_API_TOKEN_FILE or YNAB_OP_PATH is set. These values may come from direct process env, Codex config, or Claude settings.

Configuration Validation

Numeric environment variables are parsed at startup. A value that is not a number, or that falls below the minimum for its setting, is ignored: the server keeps the documented default and writes a warning to stderr naming the variable, the offending value, and the fallback it used. This covers YNAB_RATE_LIMIT_PER_HOUR, YNAB_RATE_LIMIT_BURST, YNAB_HTTP_TIMEOUT_MS, YNAB_HTTP_RETRIES, and YNAB_MAX_RESPONSE_BYTES.

Zero is a valid, documented setting for YNAB_RATE_LIMIT_PER_HOUR, YNAB_HTTP_TIMEOUT_MS, and YNAB_HTTP_RETRIES, so it is accepted rather than replaced.

Input Validation

Write tools reject over-long text before the request reaches YNAB, using the limits in YNAB's own API specification:

Payee names on transactions (payeeName): 200 characters
Payee names on create_payee and update_payee: 500 characters
Category group names: 50 characters
Memos: 500 characters

The two payee limits differ because YNAB's API sets them differently. The transaction endpoints cap payee_name at 200, while the payee endpoints cap the payee resource name at 500.

1Password Integration

If you store your YNAB token in 1Password CLI, set YNAB_OP_PATH to your secret reference and omit YNAB_API_TOKEN:

{
  "mcpServers": {
    "ynab": {
      "command": "npx",
      "args": ["-y", "@oliverames/mcp-server-for-ynab"],
      "env": {
        "YNAB_OP_PATH": "op://Personal/YNAB API Token/credential"
      }
    }
  }
}

The server invokes op read once per process when it resolves YNAB_OP_PATH. MCP hosts can start a separate process for each session, so concurrent sessions can each prompt for 1Password authorization. The server does not share a token cache between processes.

The fallback adds ~1-2s to startup. If op is unavailable or the item is not found, ynab_auth_status reports the lookup problem and returns setup guidance instead of letting a normal YNAB tool fail with a generic unauthorized error. If no token source is configured, the setup guide tells the calling agent to ask whether you have a token in 1Password or another password manager, request permission before editing agent config, and otherwise ask you to add YNAB_API_TOKEN to the appropriate Codex or Claude settings file.

Amount Handling

All amounts in tool inputs and outputs are in dollars (e.g., -12.34 for a $12.34 outflow). The server converts to/from YNAB's internal milliunits format automatically.

Direction	Sign	Example
Outflow (spending)	Negative	`-50.00`
Inflow (income)	Positive	`2500.00`
Transfer out	Negative	`-1000.00`
Transfer in	Positive	`1000.00`

Rate Limiting

The YNAB API allows 200 requests per hour per access token, enforced on a rolling window. This server applies a client-side limiter at 190 requests per hour with a burst of 10 by default. Read tools typically use one request. Write previews, fresh-state checks and verification add reads. Batch update verification uses one bounded list request, with individual lookups for older rows outside that window. Creation verification and durable workflows can read each affected entity or step. Large workflows may require later explicit recovery after interruption or rate limiting.

If a request still hits YNAB's limit (HTTP 429), the server waits for the Retry-After interval and retries automatically (up to YNAB_HTTP_RETRIES times). Transient 502/503/504 responses and network failures are retried for read requests only, since a failed write may have partially applied on the server.

Set YNAB_RATE_LIMIT_PER_HOUR=0 only for controlled local tests or smoke checks where you know you will stay under YNAB's API limit.

When the trailing-hour budget drops to 50 requests or fewer, tool responses append a pacing warning so the calling model can switch to delta requests, summary modes, and batch tools before hitting the wall.

Architecture

┌─────────────────────┐     ┌──────────────────┐     ┌──────────────┐
│  AI Assistant       │────▶│ MCP Server for   │────▶│  YNAB API    │
│                     │     │ YNAB             │     │              │
│  (Claude, GPT, etc) │◀────│ (this package)   │◀────│  api.ynab.com│
└─────────────────────┘     └──────────────────┘     └──────────────┘
         MCP                    stdio transport           HTTPS/REST

Transport: stdio (standard MCP server pattern)
Auth: Bearer token via process env, Codex or Claude agent config, YNAB_API_TOKEN_FILE, or YNAB_OP_PATH for local owner-run use
SDK: Official ynab v4.5.0 or compatible for core endpoints, with direct fetch for additional endpoints and transaction filters
Safety: read-only default, explicit write opt-in, confirmation gates for destructive and bulk-filter writes, host-pinned HTTPS requests to api.ynab.com, no redirect following, redacted token errors
Validation: All parameters validated with Zod schemas
Error handling: API errors are caught, formatted, and returned as MCP error responses with detail messages

The hosted OAuth connector runs on Cloudflare Workers at ames-ynab.link. Its implementation notes are in worker/README.md and docs/hosted-oauth-connector.md. For data handling details for the local package, see docs/privacy.md.

The Cloudflare connector is separate from a private container deployment. Its availability also depends on the YNAB application's authorization limits and approval state. Repository code doesn't establish the current upstream approval status.

Glama Hosting

The repo is ready for Glama MCP hosting: the root glama.json claims the registry listing (per Glama's glama.json spec), and the Dockerfile is what Glama's GitHub integration builds. To deploy: Glama dashboard → MCP Hosting → deploy from GitHub → select this repo, then set environment variables YNAB_API_TOKEN (required), YNAB_BUDGET_ID (recommended), and YNAB_DISABLE_AGENT_CONFIG_FALLBACK=1 (no agent config files exist in the container). Leave YNAB_ALLOW_WRITES unset until you have verified the deployment read-only, and keep the deployment private because its env vars hold your personal token. YNAB_OP_PATH is unsupported in hosted containers (no 1Password CLI); the server reports this explicitly and falls back to discovery-only mode rather than crashing. Glama wraps the stdio transport as a Streamable HTTP Gateway endpoint automatically.

Distribution Scope

The local package, hosted OAuth connector, and host-specific plugin manifests have different credential and write-access settings. Review the selected route before distributing it. Public directory approval is separate from publishing source or an npm package.

Testing

Offline Tests (no YNAB account required)

Unit tests cover the pure helpers (amount conversion, ID normalization, update verification, config parsing, URL safety, executor input validation), and the safety-model tests boot the real server over stdio to verify the read-only default, write-tool gating, annotations, and credential fallback behavior:

npm run test:unit
npm run test:safety
cd worker && npm test

The root suites run in CI (.github/workflows/ci.yml) on Node 20, 22, and 24 for pushes to main and every pull request, along with release:check and a credential-free MCP smoke test. The Worker suite covers consent-page escaping, OAuth state/PKCE, encrypted consent-scoped Durable Object credentials and CAS journals, multi-client/multi-user boundaries, refresh rotation, failed authorization rollback, and ownership-verified deletion. Legacy shared grants require deliberate reconnection after deployment.

npm run test:eval runs scripted synthetic agent trajectories through real MCP and loopback fake HTTP. It makes no model-provider calls and does not claim to benchmark model reasoning. The stateful fake suite covers imports/splits, historical delta cache, applied-write timeouts, partial failures, stale previews, undo conflicts and malicious memo instructions. See harness details and the approved coverage checklist.

Live Integration Tests

The integration test suite runs against a live YNAB budget. Most write tests create temporary transactions and delete or restore them, but category and category group creation is not reversible through the public API and is skipped unless explicitly enabled.

YNAB_API_TOKEN=your-token YNAB_BUDGET_ID=your-budget-id npm test

Use YNAB_TEST_BUDGET_ID to target a dedicated test budget without changing your server default. To include category and category group creation coverage, run with YNAB_RUN_NONREVERSIBLE_TESTS=1.

Every live write in npm test and smoke:batch-verify, including cleanup or restoration, displays a fresh exact preview and requires you to type yes in an interactive terminal. Environment flags only expose tools; they do not approve writes. Without a terminal, write calls fail before execution while read calls remain available. If cleanup is declined or a preview becomes stale, inspect the reported test transaction in YNAB. Pending bank imports cannot be previewed exactly and must be performed in YNAB.

Tests cover all tool categories: reads, reversible writes, bulk operations, search, split transactions, scheduled transaction CRUD with fetch-then-merge verification, money movements, and payee locations.

MCP Smoke Tests

Use the smoke tests when you need to prove the server is reachable over stdio without reconstructing a custom MCP client. These commands use the official MCP SDK client, the same transport shape used by normal MCP hosts. smoke:list-tools can run without a live token to verify discovery, but live read and write smokes need a token from process env, supported Codex or Claude settings, YNAB_API_TOKEN_FILE, or YNAB_OP_PATH.

YNAB_DISABLE_AGENT_CONFIG_FALLBACK=1 npm run smoke:list-tools
YNAB_API_TOKEN=your-token YNAB_BUDGET_ID=your-budget-id npm run smoke:review-unapproved
YNAB_API_TOKEN=your-token YNAB_BUDGET_ID=your-budget-id YNAB_ALLOW_WRITES=1 npm run smoke:batch-verify

To test the package currently published to npm instead of the local checkout:

YNAB_API_TOKEN=your-token YNAB_BUDGET_ID=your-budget-id npm run smoke:list-tools -- --published
YNAB_API_TOKEN=your-token YNAB_BUDGET_ID=your-budget-id npm run smoke:review-unapproved -- --published
YNAB_API_TOKEN=your-token YNAB_BUDGET_ID=your-budget-id YNAB_ALLOW_WRITES=1 npm run smoke:batch-verify -- --published

smoke:list-tools verifies that high-value read tools such as review_unapproved, get_transactions, search_transactions, search_categories, and search_payees are present. When YNAB_ALLOW_WRITES=1 is set, it also verifies update_transactions. smoke:review-unapproved calls review_unapproved with summary: true and prints only aggregate counts. smoke:batch-verify creates a temporary transaction, uses update_transactions to categorize and approve it in one call, refetches it through the MCP server, and deletes it afterward.

Development

See CONTRIBUTING.md for the local checks and pull request guidelines. Report suspected vulnerabilities through the private process in SECURITY.md.

git clone https://github.com/oliverames/ynab-mcp-server.git
cd ynab-mcp-server
npm install
YNAB_API_TOKEN=your-token npm start

Dependencies

@modelcontextprotocol/sdk - MCP server framework
ynab - Official YNAB JavaScript client
zod - Tool input and output schemas

The server uses JavaScript ES modules and has no compilation step.

Release Checks

Before publishing, run:

npm run sync:plugin
npm run release:check
npm pack --dry-run

After publishing, run npm run release:check:registry to verify the npm latest dist-tag and repo metadata agree on the same version. npm run build:mcpb remains available for an explicit local bundle, but the normal install path is direct MCP registration through npm.

Linear records the verified GitHub release and MCPB bundle in this repository's Ames Consulting (AME) release pipeline. npm publication and the hosted OAuth Worker require separate receiving checks. See release reporting for issue references, credentials and reporting-only recovery.

Pushing a v* tag triggers the release workflow (.github/workflows/release.yml), which verifies the tag against package.json, re-runs the offline tests and consistency checks, builds the MCPB bundle, and publishes a GitHub release with the bundle attached.

Privacy and Non-Affiliation

See docs/privacy.md for this connector's data handling, deletion, and token-use details.

This connector is not affiliated, associated, or in any way officially connected with YNAB or any of its subsidiaries or affiliates. The official YNAB website can be found at https://www.ynab.com.

The names YNAB and You Need A Budget, as well as related names, trade names, marks, trademarks, emblems, and images are registered trademarks of YNAB.

License

MIT

_{Built by Oliver Ames in Vermont
• GitHub
• LinkedIn
• Bluesky}

Name		Name	Last commit message	Last commit date
.antigravity-plugin		.antigravity-plugin
.claude-plugin		.claude-plugin
.github		.github
.hermes-plugin		.hermes-plugin
assets		assets
codex		codex
docs		docs
lib		lib
modules		modules
scripts		scripts
test		test
worker		worker
.dockerignore		.dockerignore
.gitignore		.gitignore
.gitleaks.toml		.gitleaks.toml
.mcp.json		.mcp.json
CONTRIBUTING.md		CONTRIBUTING.md
Dockerfile		Dockerfile
LICENSE		LICENSE
README.md		README.md
ROOT_CAUSE.md		ROOT_CAUSE.md
SECURITY.md		SECURITY.md
WORKLOG-2026-10-13.md		WORKLOG-2026-10-13.md
WORKLOG.md		WORKLOG.md
glama.json		glama.json
index.js		index.js
package-lock.json		package-lock.json
package.json		package.json
publish.sh		publish.sh
test.js		test.js

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