Bound the client-controlled limit in the extension examples

A request-sized parameter in example code should demonstrate input
bounding: Field(ge=, le=) rejects an absurd limit before the handler
allocates anything for it.

Author: maxisbey

docs/advanced/extensions.md

@@ -91,12 +91,14 @@ async def main() -> None:
 An extension can register **new request methods**: its own verbs, served next to the
 spec's:
 
-```python title="server.py" hl_lines="13-19 23 32-40"
+```python title="server.py" hl_lines="14-20 24 33-41"
 --8<-- "docs_src/extensions/tutorial002.py"
 ```
 
 * `SearchParams` subclasses `RequestParams`, so the 2026 `_meta` envelope parses
-  uniformly and your handler gets validated params, never a raw dict.
+  uniformly and your handler gets validated params, never a raw dict. Bound what
+  the client controls: `Field(ge=1, le=100)` rejects an absurd `limit` before
+  your code allocates anything for it.
 * `require_client_extension(ctx, EXTENSION_ID)` is the gate: a client that did not
   declare the extension gets the `-32021` (missing required client capability) error,
   with the machine-readable `requiredCapabilities` payload the spec asks for.

docs_src/extensions/tutorial002.py

@@ -2,6 +2,7 @@
 from typing import Any
 
 import mcp_types as types
+from pydantic import Field
 
 from mcp.server.context import ServerRequestContext
 from mcp.server.extension import Extension, MethodBinding
@@ -12,7 +13,7 @@
 
 class SearchParams(types.RequestParams):
     query: str
-    limit: int = 10
+    limit: int = Field(default=10, ge=1, le=100)
 
 
 class SearchResult(types.Result):

examples/stories/extensions/server.py

@@ -10,6 +10,7 @@
 from typing import Any
 
 import mcp_types as types
+from pydantic import Field
 
 from mcp.server.context import ServerRequestContext
 from mcp.server.extension import Extension, MethodBinding, ToolBinding
@@ -23,7 +24,7 @@ class SearchParams(types.RequestParams):
     """Subclass `RequestParams` so `_meta` (and the 2026 envelope keys) parse uniformly."""
 
     query: str
-    limit: int = 3
+    limit: int = Field(default=3, ge=1, le=25)
 
 
 class SearchResult(types.Result):