MCP Echo Service

Instructions

Implementation Reference

• src/mcp_echo/server.py:121-150 (handler)

  The main handler function for the echo_json MCP tool. It validates, analyzes, and returns the provided JSON data.

  @mcp.tool()
  async def echo_json(data: dict[str, Any], ctx: Context | None = None) -> EchoJsonResponse:
      """Echo back structured JSON data with validation and analysis.
  
      Args:
          data: The JSON data to echo back
          ctx: MCP context
  
      Returns:
          Echo response with data analysis
      """
      import json
  
      if ctx:
          await ctx.info(f"Echoing JSON data with {len(data)} keys...")
  
      # Analyze the data structure
      analysis = DataAnalysis(
          key_count=len(data),
          keys=list(data.keys()),
          data_types={key: type(value).__name__ for key, value in data.items()},
          total_size=len(json.dumps(data)),
      )
  
      return EchoJsonResponse(
          original_data=data,
          echoed_data=data,
          analysis=analysis,
          timestamp=datetime.now(UTC).isoformat(),
      )

• src/mcp_echo/api_models.py:39-45 (schema)

  The Pydantic schema defining the response structure for the echo_json tool.

  class EchoJsonResponse(BaseModel):
      """Response model for echo_json tool."""
  
      original_data: dict[str, Any] = Field(..., description="The original JSON data sent")
      echoed_data: dict[str, Any] = Field(..., description="The echoed JSON data")
      analysis: DataAnalysis = Field(..., description="Analysis of the data structure")
      timestamp: str = Field(..., description="ISO 8601 timestamp of the operation")