A2A endpoints & methods

Overview

All Warden Agents are immediately compatible with the A2A protocol, supporting the Agent Card and the JSON-RPC endpoint with the core methods.

To learn more, see the A2A specification.

For usage examples, see Test the Agent locally and Host your Agent.

Get Agent Card

Name	Method	Endpoint
Get Agent Card	GET	/.well-known/agent-card.json

An A2A Agent Card is a JSON file that describes your Agent's capabilities. It enables clients and other Agents to discover and understand what the Agent can do.

tip

You can change this metadata at any moment, as explained in Update the Agent Card.

Typically, Agent Cards look like this:

{
    "name": "general-test",
    "description": "A helpful AI agent named general-test",
    "url": "http://localhost:3000",
    "version": "0.1.0",
    "capabilities": {
        "streaming": true,
        "multiTurn": false
    },
    "skills": [],
    "defaultInputModes": [
        "text"
    ],
    "defaultOutputModes": [
        "text"
    ]
}

JSON-RPC endpoint

The A2A JSON-RPC endpoint allows initiating various A2A operations such as sending messages and managing tasks. It uses just the base URL:

Name	Method	Endpoint
A2A JSON-RPC	POST	/

To run a particular A2A method, specify it in the JSON-RPC request body:

Name	JSON-RPC method
Send Message	message/send
Send Streaming Message	message/stream
Get Task	tasks/get
Cancel Task	tasks/cancel
Subscribe to Task	tasks/resubscribe

You can find detailed descriptions of each method in the sections below.

Send Message

Postman

POST BASE_URL
Headers: Content-Type: application/json
Authorization: Type: Bearer Token, Token: AGENT_API_KEY
Body:

{
  "jsonrpc": "2.0",
  "id": "",
  "method": "message/send",
  "params": {
    "message": {
      "role": "user",
      "parts": [
        {
          "kind": "text",
          "text": "PROMPT_TEXT"
        }
      ],
      "messageId": ""
    },
    "thread": {
      "threadId": ""
    }
  }
}

cURL

curl BASE_URL \
  --request POST \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer AGENT_API_KEY' \
  --data '{
    "jsonrpc": "2.0",
    "id": "",
    "method": "message/send",
    "params": {
      "message": {
        "role": "user",
        "parts": [
          {
            "kind": "text",
            "text": "PROMPT_TEXT"
          }
        ],
        "messageId": ""
      },
      "thread": {
        "threadId": ""
      }
    }
  }'

tip

This method returns a result object containing the LLM response, conversation history, and execution status. Task methods require the task ID, which is returned as result.id.

Send Streaming Message

Postman

POST BASE_URL
Headers: Content-Type: application/json
Authorization: Type: Bearer Token, Token: AGENT_API_KEY
Body:

{
  "jsonrpc": "2.0",
  "id": "",
  "method": "message/stream",
  "params": {
    "message": {
      "role": "user",
      "parts": [
        {
          "kind": "text",
          "text": "PROMPT_TEXT"
        }
      ],
      "messageId": ""
    },
    "thread": {
      "threadId": ""
    }
  }
}

cURL

curl BASE_URL \
  --request POST \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer AGENT_API_KEY' \
  --data '{
    "jsonrpc": "2.0",
    "id": "",
    "method": "message/stream",
    "params": {
      "message": {
        "role": "user",
        "parts": [
          {
            "kind": "text",
            "text": "PROMPT_TEXT"
          }
        ],
        "messageId": ""
      },
      "thread": {
        "threadId": ""
      }
    }
  }'

tip

This method streams task status updates. When the response is ready, the stream includes the generated LLM message. Task methods require the task ID, which is returned as result.id.

Get Task

Postman

POST BASE_URL
Headers: Content-Type: application/json
Authorization: Type: Bearer Token, Token: AGENT_API_KEY
Body:

{
  "jsonrpc": "2.0",
  "id": "",
  "method": "tasks/get",
  "params": {
    "id": ""
  }
}

cURL

curl BASE_URL \
  --request POST \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer AGENT_API_KEY' \
  --data '{
    "jsonrpc": "2.0",
    "id": "",
    "method": "tasks/get",
    "params": {
      "id": "TASK_ID"
    }
  }'

tip

In params.id, specify the task ID. You can obtain this value from result.id, returned by Send Message or Send Streaming Message.

Cancel Task

Postman

POST BASE_URL
Headers: Content-Type: application/json
Authorization: Type: Bearer Token, Token: AGENT_API_KEY
Body:

{
  "jsonrpc": "2.0",
  "id": "",
  "method": "tasks/cancel",
  "params": {
    "id": "TASK_ID"
  }
}

cURL

curl BASE_URL \
  --request POST \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer AGENT_API_KEY' \
  --data '{
    "jsonrpc": "2.0",
    "id": "",
    "method": "tasks/cancel",
    "params": {
      "id": "TASK_ID"
    }
  }'

tip

In params.id, specify the task ID. You can obtain this value from result.id, returned by Send Message or Send Streaming Message.

Subscribe to Task

Postman

POST BASE_URL
Headers: Content-Type: application/json
Authorization: Type: Bearer Token, Token: AGENT_API_KEY
Body:

{
  "jsonrpc": "2.0",
  "id": "",
  "method": "tasks/resubscribe",
  "params": {
    "id": "TASK_ID"
  }
}

cURL

curl BASE_URL \
  --request POST \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer AGENT_API_KEY' \
  --data '{
    "jsonrpc": "2.0",
    "id": "",
    "method": "tasks/resubscribe",
    "params": {
      "id": "TASK_ID"
    }
  }'

tip

In params.id, specify the task ID. You can obtain this value from result.id, returned by Send Message or Send Streaming Message.