The 1.x commitment covers this project's documented tool and CLI interfaces. Substack's underlying endpoints remain undocumented and can change independently. See the output contract and draft update migration.
This server imposes no Bestseller requirement or paid-plan check. Use an account with the permissions needed for the requested publication operation. Having a Substack account alone does not grant access to another publication's drafts, analytics or subscribers. Account tier coverage has not been independently verified across every Substack plan.
The opt-in live read probe at source revision
601b9b53315d0814a76cf45fbf4eae8d093ce93e (PR #88, before the 1.0 version bump)
passed publication metadata, draft-list and subscriber-count checks against one
custom-domain publication on September 8, 2026 at 05:19 UTC. It made five read
requests and no writes. This establishes authenticated
read access for that configuration; it does not verify account identity, tier,
every endpoint or a different publication. Automated fixtures cover malformed
responses, expired authentication, publication isolation and bounded failures.
| Surface | Verification for the 1.0 release | Limit |
|---|---|---|
| Claude Code | Local marketplace installation and MCP connection; model-driven list_drafts call with synthetic data |
Does not establish Claude Desktop GUI setup |
| Codex CLI 0.153.4 | Configured stdio server, model-driven list_drafts call and checked tool result with synthetic data |
Codex app plugin installation is not independently verified |
| MCP SDK | Installed npm package initialization, complete catalog, object/text results and read-only probe | A protocol check does not establish every client UI |
| Streamable HTTP | Container initialization/catalog and missing/wrong bearer rejection | Deployment must provide its own access controls and TLS where appropriate |
| Session profiles | Legacy migration, rollback and explicit multi-publication selection tests | Machine-bound files are not portable; manual browser-login UI remains an integration limit |
Use the README setup and plugin guide. Local stdio plugins are not hosted ChatGPT connectors. A hosted service with per-user authentication and session custody requires separate work. MCPB is deferred: npm, the CLI and local plugins share one maintained installation path; a desktop bundle needs its own packaging and upgrade verification first.
1.0 retains per-post analytics and subscriber counts, including their CLI read commands. Aggregate dashboards, post ranking, segmentation and bulk subscriber export remain in #52. Prioritize additions against concrete creator questions and verifiable endpoint behavior as feedback arrives. Newsletter-user feedback is a post-release input, not a prerequisite for the stability release.
Long-form posts remain draft-only. Draft replacement requires a reviewed plan and remains subject to the documented residual race and readback limitations. Notes publish immediately; image uploads can expose a public URL. Subscriber additions require consent and default to dry-run. These are distinct side effects and need appropriate authorization in the calling application.
Remote image fetching, community interactions, an OS keychain backend, MCPB and hosted multi-tenant operation are outside 1.0. Container support starts with Linux amd64; see containers for public-artifact verification and the separate OCI attestation follow-up.
A documented JavaScript/TypeScript library API is not part of the 1.x interface. It was evaluated and deferred; see TypeScript API evaluation for the proposed surface and the conditions for revisiting it.