PyMCP

Instructions

Implementation Reference

• src/pymcp/server.py:264-304 (handler)

  The main handler function for the 'vonmises_random' tool. It takes mu as input, elicits kappa from the user, validates it, and returns a random sample from the von Mises distribution using Python's random.vonmisesvariate.

  async def vonmises_random(
      self,
      ctx: Context,
      mu: Annotated[
          float,
          Field(
              description="The mean angle mu (μ), expressed in radians between 0 and 2π",
              ge=0,
              le=2 * math.pi,
          ),
      ],
  ) -> float:
      """Generate a random number from the von Mises distribution. This is an example of a tool that uses elicitation to obtain the required parameter kappa (κ)."""
      await ctx.info("Requesting the user for the value of kappa for von Mises distribution.")
      response = await ctx.elicit(
          message="Please provide the value of kappa (κ) for the von Mises distribution. It should be a positive number.",
          response_type=float,
      )
      kappa: float = 1.0  # Default value
      match response:  # pragma: no cover
          case AcceptedElicitation(data=kappa):  # type: ignore[misc]
              await ctx.warning(f"Received kappa: {kappa}")
              if kappa < 0:
                  raise McpError(
                      error=ErrorData(
                          code=INVALID_PARAMS,
                          message="kappa (κ) must be a positive number.",
                      )
                  )
          case DeclinedElicitation():  # type: ignore[misc]
              await ctx.warning("User declined to provide kappa (κ). Using default value of 1.0.")
          case CancelledElicitation():  # type: ignore[misc]
              await ctx.warning("User cancelled the operation. The random number will NOT be generated.")
              raise McpError(
                  error=ErrorData(
                      code=INVALID_PARAMS,
                      message="Operation cancelled by the user.",
                  )
              )
      return random.vonmisesvariate(mu, kappa)

• src/pymcp/server.py:267-275 (schema)

  Pydantic-based input schema definition for the 'mu' parameter, including description and range constraints (0 to 2π). Kappa is elicited at runtime.

      mu: Annotated[
          float,
          Field(
              description="The mean angle mu (μ), expressed in radians between 0 and 2π",
              ge=0,
              le=2 * math.pi,
          ),
      ],
  ) -> float:

• src/pymcp/server.py:72-72 (registration)

  Tool registration entry in the PyMCP class 'tools' list, specifying the function name and tags.

  {"fn": "vonmises_random", "tags": ["experimental", "elicitation", "example"]},