Debug-MCP

Instructions

Implementation Reference

• src/mcp_debug_tool/server.py:555-610 (handler)

  The handler function for the 'sessions_step_in' tool. Extracts sessionId from arguments, calls session_manager.step_in_async(session_id), serializes the response to JSON, and handles various errors by returning appropriate JSON error messages.

  async def _handle_sessions_step_in(self, arguments: dict) -> list[TextContent]:
      """
      Handler for sessions_step_in tool.
      
      Steps into the next function call.
      """
      try:
          session_id = arguments.get("sessionId")
          if not session_id:
              return [
                  TextContent(
                      type="text",
                      text=json.dumps({
                          "error": {
                              "type": "ValueError",
                              "message": "sessionId is required",
                          }
                      }),
                  )
              ]
  
          response = await self.session_manager.step_in_async(session_id)
          result = response.model_dump()
  
          return [
              TextContent(
                  type="text",
                  text=json.dumps(result),
              )
          ]
      except KeyError as e:
          return [
              TextContent(
                  type="text",
                  text=json.dumps({
                      "error": {
                          "type": "SessionNotFound",
                          "message": str(e),
                      }
                  }),
              )
          ]
      except Exception as e:
          logger.exception("Error in step_in")
          return [
              TextContent(
                  type="text",
                  text=json.dumps({
                      "error": {
                          "type": type(e).__name__,
                          "message": str(e),
                      }
                  }),
              )
          ]

• src/mcp_debug_tool/server.py:162-175 (registration)

  Registration of the 'sessions_step_in' MCP tool, including name, description, and input schema requiring 'sessionId'.

  Tool(
      name="sessions_step_in",
      description="Step into the next function call (requires active breakpoint)",
      inputSchema={
          "type": "object",
          "properties": {
              "sessionId": {
                  "type": "string",
                  "description": "The debug session ID",
              },
          },
          "required": ["sessionId"],
      },
  ),

• src/mcp_debug_tool/server.py:165-174 (schema)

  Input schema for the 'sessions_step_in' tool, defining a required 'sessionId' string parameter.

  inputSchema={
      "type": "object",
      "properties": {
          "sessionId": {
              "type": "string",
              "description": "The debug session ID",
          },
      },
      "required": ["sessionId"],
  },