From 57659d07a7248fd57ebe2a708dd60fe97e77c70a Mon Sep 17 00:00:00 2001
From: heznpc <heznpc@gmail.com>
Date: Sat, 2 May 2026 10:44:12 +0900
Subject: [PATCH] feat: enforce greet(name) input constraints via
 pydantic.Field
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Audit (2026-05-01, P2.16): the TS sibling validates greet's name with
Zod (1–200 chars). Python equivalent was untyped — empty strings and
megastring inputs reached the handler.

Switch the parameter annotation from `name: str` to
`name: Annotated[str, Field(min_length=1, max_length=200, description=...)]`.
FastMCP picks up the Annotated metadata and emits the constraint into
the tool's JSON schema, so violations are rejected at protocol level.

Tests pass; mypy strict still clean.
---
 src/my_mcp_server/server.py | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/my_mcp_server/server.py b/src/my_mcp_server/server.py
index 65ec224..d615a5e 100644
--- a/src/my_mcp_server/server.py
+++ b/src/my_mcp_server/server.py
@@ -6,9 +6,11 @@
 
 import logging
 import os
+from typing import Annotated
 
 from mcp.server.fastmcp import FastMCP
 from mcp.types import ToolAnnotations
+from pydantic import Field
 
 from my_mcp_server.prompts.code_review import register as register_code_review
 from my_mcp_server.resources.server_info import register as register_server_info
@@ -60,14 +62,22 @@ def err(message: str) -> dict[str, object]:
         openWorldHint=False,
     ),
 )
-async def greet(name: str) -> str:
+async def greet(
+    name: Annotated[
+        str,
+        Field(
+            min_length=1,
+            max_length=200,
+            description="Name to greet (1–200 characters).",
+        ),
+    ],
+) -> str:
     """Greet someone by name.
 
-    Args:
-        name: Name to greet.
-
-    Returns:
-        A greeting message.
+    The Annotated[..., Field(...)] form propagates the constraint into
+    FastMCP's generated JSON schema, so empty strings and oversized inputs
+    are rejected by the protocol layer before the handler runs. The TS
+    sibling enforces the same shape via Zod.
     """
     logger.info("Greeting %s", name)
     return f"Hello, {name}!"