MCP Background Task Server

Instructions

Implementation Reference

• src/index.ts:225-248 (handler)

  Handler function that fetches the stderr output from the Child process instance for the given task name and returns it in the tool response format.

  async ({ name }) => {
    const child = processes.get(name);
    if (!child) {
      return {
        content: [
          {
            type: "text",
            text: `No task found with name "${name}".`,
          },
        ],
      };
    }
  
    return {
      content: [
        {
          type: "text",
          text: `Stderr of task "${name}":\n${
            child.stderr || "No error output yet."
          }`,
        },
      ],
    };
  }

• src/index.ts:218-224 (schema)

  Schema definition for the get-task-stderr tool, including title, description, and input schema requiring a task name.

  {
    title: "Get Task Stderr",
    description: "Retrieves the stderr of a running background task.",
    inputSchema: {
      name: z.string().describe("Unique name of the task"),
    },
  },

• src/index.ts:216-249 (registration)

  Registration of the get-task-stderr tool with the MCP server, including schema and handler.

  server.registerTool(
    "get-task-stderr",
    {
      title: "Get Task Stderr",
      description: "Retrieves the stderr of a running background task.",
      inputSchema: {
        name: z.string().describe("Unique name of the task"),
      },
    },
    async ({ name }) => {
      const child = processes.get(name);
      if (!child) {
        return {
          content: [
            {
              type: "text",
              text: `No task found with name "${name}".`,
            },
          ],
        };
      }
  
      return {
        content: [
          {
            type: "text",
            text: `Stderr of task "${name}":\n${
              child.stderr || "No error output yet."
            }`,
          },
        ],
      };
    }
  );

• src/index.ts:22-24 (helper)

  Event listener that accumulates stderr output from the child process into the Child instance's stderr property.

  child.stderr?.on("data", (data) => {
    this.stderr += data.toString();
  });

• src/index.ts:37-38 (helper)

  Getter method for accessing the accumulated stderr of a Child process instance.

  public getStderr(): string {
    return this.stderr;