一文看懂Google的A2A协议以及与MCP的区别

// An AgentCard conveys key information:
// - Overall details (version, name, description, uses)
// - Skills: A set of capabilities the agent can perform
// - Default modalities/content types supported by the agent.
// - Authentication requirements
interface AgentCard {
// Human readable name of the agent.
// (e.g. "Recipe Agent")
  name: string;
// A human-readable description of the agent. Used to assist users and
// other agents in understanding what the agent can do.
// (e.g. "Agent that helps users with recipes and cooking.")
  description: string;
// A URL to the address the agent is hosted at.
  url: string;
// The service provider of the agent
  provider?: {
    organization: string;
    url: string;
  };
// The version of the agent - format is up to the provider. (e.g. "1.0.0")
  version: string;
// A URL to documentation for the agent.
  documentationUrl?: string;
// Optional capabilities supported by the agent.
  capabilities: {
    streaming?: boolean; // true if the agent supports SSE
    pushNotifications?: boolean; // true if the agent can notify updates to client
    stateTransitionHistory?: boolean; //true if the agent exposes status change history for tasks
  };
// Authentication requirements for the agent.
// Intended to match OpenAPI authentication structure.
  authentication: {
    schemes: string[]; // e.g. Basic, Bearer
    credentials?: string; //credentials a client should use for private cards
  };
// The set of interaction modes that the agent
// supports across all skills. This can be overridden per-skill.
  defaultInputModes: string[]; // supported mime types for input
  defaultOutputModes: string[]; // supported mime types for output
// Skills are a unit of capability that an agent can perform.
  skills: {
    id: string; // unique identifier for the agent's skill
    name: string; //human readable name of the skill
    // description of the skill - will be used by the client or a human
    // as a hint to understand what the skill does.
    description: string;
    // Set of tagwords describing classes of capabilities for this specific
    // skill (e.g. "cooking", "customer support", "billing")
    tags: string[];
    // The set of example scenarios that the skill can perform.
    // Will be used by the client as a hint to understand how the skill can be
    // used. (e.g. "I need a recipe for bread")
    examples?: string[]; // example prompts for tasks
    // The set of interaction modes that the skill supports
    // (if different than the default)
    inputModes?: string[]; // supported mime types for input
    outputModes?: string[]; // supported mime types for output
  }[];
}

interface Task {
  id: string; // unique identifier for the task
  sessionId: string; // client-generated id for the session holding the task.
  status: TaskStatus; // current status of the task
  history?: Message[];
  artifacts?: Artifact[]; // collection of artifacts created by the agent.
  metadata?: Record<string, any>; // extension metadata
}
// TaskState and accompanying message.
interface TaskStatus {
  state: TaskState;
  message?: Message; //additional status updates for client
  timestamp?: string; // ISO datetime value
}
// sent by server during sendSubscribe or subscribe requests
interface TaskStatusUpdateEvent {
  id: string;
  status: TaskStatus;
  final: boolean; //indicates the end of the event stream
  metadata?: Record<string, any>;
}
// sent by server during sendSubscribe or subscribe requests
interface TaskArtifactUpdateEvent {
  id: string;
  artifact: Artifact;
  metadata?: Record<string, any>;
}
// Sent by the client to the agent to create, continue, or restart a task.
interface TaskSendParams {
  id: string;
  sessionId?: string; //server creates a new sessionId for new tasks if not set
  message: Message;
  historyLength?: number; //number of recent messages to be retrieved
// where the server should send notifications when disconnected.
  pushNotification?: PushNotificationConfig;
  metadata?: Record<string, any>; // extension metadata
}
type TaskState =
  | "submitted"
  | "working"
  | "input-required"
  | "completed"
  | "canceled"
  | "failed"
  | "unknown";

interface Artifact {
  name?: string;
  description?: string;
  parts: Part[];
  metadata?: Record<string, any>;
  index: number;
  append?: boolean;
  lastChunk?: boolean;
}

interface Message {
  role: "user" | "agent";
  parts: Part[];
  metadata?: Record<string, any>;
}

interface TextPart {
type: "text";
  text: string;
}
interface FilePart {
type: "file";
  file: {
    name?: string;
    mimeType?: string;
    // oneof {
    bytes?: string; //base64 encoded content
    uri?: string;
    //}
  };
}
interface DataPart {
type: "data";
  data: Record<string, any>;
}
type Part = (TextPart | FilePart | DataPart) & {
  metadata: Record<string, any>;
};

interface PushNotificationConfig {
  url: string;
  token?: string; // token unique to this task/session
  authentication?: {
    schemes: string[];
    credentials?: string;
  };
}
interface TaskPushNotificationConfig {
  id: string; //task id
  pushNotificationConfig: PushNotificationConfig;
}

//agent card
{
"name": "Google Maps Agent",
"description": "Plan routes, remember places, and generate directions",
"url": "https://maps-agent.google.com",
"provider": {
    "organization": "Google",
    "url": "https://google.com"
  },
"version": "1.0.0",
"authentication": {
    "schemes": "OAuth2"
  },
"defaultInputModes": ["text/plain"],
"defaultOutputModes": ["text/plain", "application/html"],
"capabilities": {
    "streaming": true,
    "pushNotifications": false
  },
"skills": [
    {
      "id": "route-planner",
      "name": "Route planning",
      "description": "Helps plan routing between two locations",
      "tags": ["maps", "routing", "navigation"],
      "examples": [
        "plan my route from Sunnyvale to Mountain View",
        "what's the commute time from Sunnyvale to San Francisco at 9AM",
        "create turn by turn directions from Sunnyvale to Mountain View"
      ],
      // can return a video of the route
      "outputModes": ["application/html", "video/mp4"]
    },
    {
      "id": "custom-map",
      "name": "My Map",
      "description": "Manage a custom map with your own saved places",
      "tags": ["custom-map", "saved-places"],
      "examples": [
        "show me my favorite restaurants on the map",
        "create a visual of all places I've visited in the past year"
      ],
      "outputModes": ["application/html"]
    }
  ]
}

//Request
{
"jsonrpc": "2.0",
"id": 1,
"method":"tasks/send",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "message": {
      "role":"user",
      "parts": [{
        "type":"text",
        "text": "tell me a joke"
      }]
    },
    "metadata": {}
  }
}
//Response
{
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "completed",
    },
    "artifacts": [{
      "name":"joke",
      "parts": [{
          "type":"text",
          "text":"Why did the chicken cross the road? To get to the other side!"
        }]
      }],
    "metadata": {}
  }
}

//Request
{
"jsonrpc": "2.0",
"id": 1,
"method":"tasks/get",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "historyLength": 10,
    "metadata": {}
  }
}
//Response
{
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "completed"
    },
    "artifacts": [{
      "parts": [{
        "type":"text",
        "text":"Why did the chicken cross the road? To get to the other side!"
      }]
    }],
    "history":[
      {
        "role": "user",
        "parts": [
          {
            "type": "text",
            "text": "tell me a joke"
          }
        ]
      }
    ],
    "metadata": {}
  }
}

//Request
{
"jsonrpc": "2.0",
"id": 1,
"method":"tasks/cancel",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "metadata": {}
  }
}
//Response
{
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "canceled"
    },
    "metadata": {}
  }
}

//Request
{
"jsonrpc": "2.0",
"id": 1,
"method":"tasks/pushNotification/set",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "pushNotificationConfig": {
      "url": "https://example.com/callback",
      "authentication": {
        "schemes": ["jwt"]
      }
    }
  }
}
//Response
{
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "pushNotificationConfig": {
      "url": "https://example.com/callback",
      "authentication": {
        "schemes": ["jwt"]
      }
    }
  }
}

//Request
{
"jsonrpc": "2.0",
"id": 1,
"method":"tasks/pushNotification/get",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64"
  }
}
//Response
{
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "pushNotificationConfig": {
      "url": "https://example.com/callback",
      "authentication": {
        "schemes": ["jwt"]
      }
    }
  }
}

//Request - seq 1
{
"jsonrpc": "2.0",
"id": 1,
"method":"tasks/send",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "message": {
      "role":"user",
      "parts": [{
        "type":"text",
        "text": "request a new phone for me"
      }]
    },
    "metadata": {}
  }
}
//Response - seq 2
{
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "input-required",
      "message": {
        "parts": [{
          "type":"text",
          "text":"Select a phone type (iPhone/Android)"
        }]
      }
    },
    "metadata": {}
  }
}
//Request - seq 3
{
"jsonrpc": "2.0",
"id": 2,
"method":"tasks/send",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "message": {
      "role":"user",
      "parts": [{
        "type":"text",
        "text": "Android"
      }]
    },
    "metadata": {}
  }
}
//Response - seq 4
{
"jsonrpc": "2.0",
"id": 2,
"result": {
    "id": 1,
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "completed"
    },
    "artifacts": [{
      "name": "order-confirmation",
      "parts": [{
          "type":"text",
          "text":"I have ordered a new Android device for you. Your request number is R12443"
        }],
      "metadata": {}
    }],
    "metadata": {}
  }
}

//Request
{
"method":"tasks/sendSubscribe",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "message": {
      "role":"user",
      "parts": [{
        "type":"text",
        "text": "write a long paper describing the attached pictures"
      },{
        "type":"file",
        "file": {
           "mimeType": "image/png",
           "data":"<base64-encoded-content>"
        }
      }]
    },
    "metadata": {}
  }
}

//Response
data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "status": {
      "state": "working",
      "timestamp":"2025-04-02T16:59:25.331844"
    },
    "final": false
  }
}

data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "artifact": [
      "parts": [
        {"type":"text", "text": "<section 1...>"}
      ],
      "index": 0,
      "append": false,
      "lastChunk": false
    ]
  }
}
data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "artifact": [
      "parts": [
        {"type":"text", "text": "<section 2...>"}
      ],
      "index": 0,
      "append": true,
      "lastChunk": false
    ]
  }
}
data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "artifact": [
      "parts": [
        {"type":"text", "text": "<section 3...>"}
      ],
      "index": 0,
      "append": true,
      "lastChunk": true
    ]
  }
}

data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "status": {
      "state": "completed",
      "timestamp":"2025-04-02T16:59:35.331844"
    },
    "final": true
  }
}

//Request
{
"method":"tasks/resubscribe",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "metadata": {}
  }
}
//Response
data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "artifact":[
      "parts": [
        {"type":"text", "text": "<section 2...>"}
      ],
      "index": 0,
      "append": true,
      "lastChunk":false
    ]
  }
}
data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "artifact":[
      "parts": [
        {"type":"text", "text": "<section 3...>"}
      ],
      "index": 0,
      "append": true,
      "lastChunk": true
    ]
  }
}

data: {
"jsonrpc": "2.0",
"id": 1,
"result": {
    "id": 1,
    "status": {
      "state": "completed",
      "timestamp":"2025-04-02T16:59:35.331844"
    },
    "final": true
  }
}

//Request - seq 1
{
"jsonrpc": "2.0",
"id": 9,
"method":"tasks/send",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "message": {
      "role":"user",
      "parts": [{
        "type":"text",
        "text": "Analyze the attached report and generate high level overview"
      },{
        "type":"file",
        "file": {
           "mimeType": "application/pdf",
           "data":"<base64-encoded-content>"
        }
      }]
    },
    "metadata": {}
  }
}
//Response - seq 2
{
"jsonrpc": "2.0",
"id": 9,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "working",
      "message": {
        "role": "agent",
        "parts": [{
          "type":"text",
          "text":"analysis in progress, please wait"
        }],
        "metadata": {}
       }
     },
    "metadata": {}
  }
}
//Request - seq 3
{
"jsonrpc": "2.0",
"id": 10,
"method":"tasks/get",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "metadata": {}
  }
}
//Response - seq 4
{
"jsonrpc": "2.0",
"id": 9,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "completed"
     },
    "artifacts": [{
      "parts": [{
        "type":"text",
        "text":"<generated analysis content>"
       }],
       "metadata": {}
     }],
    "metadata": {}
  }
}

//Request
{
"jsonrpc": "2.0",
"id": 9,
"method":"tasks/send",
"params": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "message": {
      "role":"user",
      "parts": [{
        "type":"text",
        "text": "Show me a list of my open IT tickets",
        "metadata": {
          "mimeType": "application/json",
          "schema": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "ticketNumber": { "type": "string" },
                "description": { "type": "string" }
              }
            }
          }
        }
      }]
    },
    "metadata": {}
  }
}
//Response
{
"jsonrpc": "2.0",
"id": 9,
"result": {
    "id": "de38c76d-d54c-436c-8b9f-4c2703648d64",
    "sessionId": "c295ea44-7543-4f78-b524-7a38915ad6e4",
    "status": {
      "state": "working",
      "message": {
        "role": "agent",
        "parts": [{
            "type":"text",
            "text":"[{\"ticketNumber\":\"REQ12312\",\"description\":\"request for VPN access\"},{\"ticketNumber\":\"REQ23422\",\"description\":\"Add to DL - team-gcp-onboarding\"}]"
        }],
        "metadata": {}
      }
    },
    "metadata": {}
  }
}

interface ErrorMessage {
  code: number;
  message: string;
  data?: any;
}