A2A Client MCP Server

Instructions

Implementation Reference

• index.ts:73-90 (schema)

  Tool schema definition including name, description, and input schema for a2a_cancel_task.

  {
    name: "a2a_cancel_task",
    description: "Cancel a running task",
    inputSchema: {
      type: "object",
      properties: {
        taskId: {
          type: "string",
          description: "ID of the task to cancel",
        },
        agentId: {
          type: "string",
          description: "ID of the agent that is handling the task",
        },
      },
      required: ["taskId", "agentId"],
    },
  },

• index.ts:183-200 (handler)

  Primary MCP tool handler for a2a_cancel_task: extracts parameters, retrieves A2A client, calls cancelTask method, and formats response.

  case "a2a_cancel_task": {
    const { taskId, agentId } = args as { taskId: string; agentId: string };
    const client = agentManager.getClientById(agentId);
    
    if (!client) {
      throw new Error(`No agent found with ID ${agentId}`);
    }
  
    const result = await client.cancelTask({ id: taskId });
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(result, null, 2),
        },
      ],
    };
  }

• a2a-client.ts:422-425 (handler)

  Core implementation of task cancellation in A2AClient: sends HTTP request to tasks/cancel endpoint and processes JSON response.

  async cancelTask(params: TaskIdParams): Promise<Task | null> {
    const httpResponse = await this._makeHttpRequest("tasks/cancel", params);
    return this._handleJsonResponse<Task | null>(httpResponse, "tasks/cancel");
  }

• agent-manager.ts:29-31 (helper)

  AgentManager method to retrieve A2AClient instance by agent ID, used in the tool handler.

  getClientById(id: string): A2AClient | undefined {
    return this.clients.get(id);
  }