PyMCP

Instructions

Implementation Reference

• src/pymcp/server.py:218-252 (handler)

  The main handler function for the 'permutations' tool, which calculates the permutation P(n, k) = n! / (n-k)! using math.perm, with validation for parameters n and k.

  async def permutations(
      self,
      ctx: Context,
      n: Annotated[
          int,
          Field(
              ge=1,
              description="The number of items to choose from.",
          ),
      ],
      k: Annotated[
          int | None,
          Field(
              default=None,
              ge=1,
              description="The optional number of items to choose.",
          ),
      ],
  ) -> int:
      """Calculate the number of ways to choose k items from n items without repetition and with order."""
      """If k is not provided, it defaults to n."""
      assert isinstance(n, int) and n >= 1, "n must be a positive integer."
  
      if k is None:
          k = n
      if k > n:
          raise McpError(
              error=ErrorData(
                  code=INVALID_PARAMS,
                  message=f"k ({k}) cannot be greater than n ({n}).",
              )
          )
  
      return math.perm(n, k)

• src/pymcp/server.py:66-70 (registration)

  Registration entry for the 'permutations' tool in the PyMCP class tools list, including tags and annotations.

  {
      "fn": "permutations",
      "tags": ["math", "permutation", "example"],
      "annotations": {"readOnlyHint": True},
  },

• src/pymcp/server.py:414-414 (registration)

  Inclusion of 'permutations' tool in the response caching middleware settings.

  included_tools=["greet", "permutations"],

• src/pymcp/server.py:221-252 (schema)

  Pydantic schema definitions for input parameters n and k of the permutations tool, including constraints and descriptions.

      n: Annotated[
          int,
          Field(
              ge=1,
              description="The number of items to choose from.",
          ),
      ],
      k: Annotated[
          int | None,
          Field(
              default=None,
              ge=1,
              description="The optional number of items to choose.",
          ),
      ],
  ) -> int:
      """Calculate the number of ways to choose k items from n items without repetition and with order."""
      """If k is not provided, it defaults to n."""
      assert isinstance(n, int) and n >= 1, "n must be a positive integer."
  
      if k is None:
          k = n
      if k > n:
          raise McpError(
              error=ErrorData(
                  code=INVALID_PARAMS,
                  message=f"k ({k}) cannot be greater than n ({n}).",
              )
          )
  
      return math.perm(n, k)