SendMessageResponse

Represents the response for the message.send method.

JSON representation 
{

  // Union field payload can be only one of the following:
  "task": {
    object (Task)
  },
  "message": {
    object (Message)
  }
  // End of list of possible types for union field payload.
}
Fields
Union field payload. The payload of the response. payload can be only one of the following:
task

object (Task)

The task created or updated by the message.
message

object (Message)

A message from the agent.

Task

Task is the core unit of action for A2A. It has a current status and when results are created for the task they are stored in the artifact. If there are multiple turns for a task, these are stored in history.

JSON representation 
{
  "id": string,
  "contextId": string,
  "status": {
    object (TaskStatus)
  },
  "artifacts": [
    {
      object (Artifact)
    }
  ],
  "history": [
    {
      object (Message)
    }
  ],
  "metadata": {
    object
  }
}
Fields
id

string

Required. Unique identifier (e.g. UUID) for the task, generated by the server for a new task.
contextId

string

Unique identifier (e.g. UUID) for the contextual collection of interactions (tasks and messages).
status

object (TaskStatus)

Required. The current status of a Task, including state and a message.
artifacts[]

object (Artifact)

A set of output artifacts for a Task.
history[]

object (Message)

protolint:disable REPEATED_FIELD_NAMES_PLURALIZED The history of interactions from a Task.
metadata

object (Struct format)

protolint:enable REPEATED_FIELD_NAMES_PLURALIZED A key/value object to store custom metadata about a task.

TaskStatus

A container for the status of a task

JSON representation 
{
  "state": enum (TaskState),
  "message": {
    object (Message)
  },
  "timestamp": string
}
Fields
state

enum (TaskState)

Required. The current state of this task.
message

object (Message)

A message associated with the status.
timestamp

string (Timestamp format)

ISO 8601 Timestamp when the status was recorded. Example: "2023-10-27T10:00:00Z"

Uses RFC 3339, where generated output will always be Z-normalized and use 0, 3, 6 or 9 fractional digits. Offsets other than "Z" are also accepted. Examples: "2014-10-02T15:01:23Z", "2014-10-02T15:01:23.045123456Z" or "2014-10-02T15:01:23+05:30".

TaskState

Defines the possible lifecycle states of a Task.

Enums
TASK_STATE_UNSPECIFIED The task is in an unknown or indeterminate state.
TASK_STATE_SUBMITTED Indicates that a task has been successfully submitted and acknowledged.
TASK_STATE_WORKING Indicates that a task is actively being processed by the agent.
TASK_STATE_COMPLETED Indicates that a task has finished successfully. This is a terminal state.
TASK_STATE_FAILED Indicates that a task has finished with an error. This is a terminal state.
TASK_STATE_CANCELED Indicates that a task was canceled before completion. This is a terminal state.
TASK_STATE_INPUT_REQUIRED Indicates that the agent requires additional user input to proceed. This is an interrupted state.
TASK_STATE_REJECTED Indicates that the agent has decided to not perform the task. This may be done during initial task creation or later once an agent has determined it can't or won't proceed. This is a terminal state.
TASK_STATE_AUTH_REQUIRED Indicates that authentication is required to proceed. This is an interrupted state.

Artifact

Artifacts represent task outputs.

JSON representation 
{
  "artifactId": string,
  "name": string,
  "description": string,
  "parts": [
    {
      object (Part)
    }
  ],
  "metadata": {
    object
  },
  "extensions": [
    string
  ]
}
Fields
artifactId

string

Required. Unique identifier (e.g. UUID) for the artifact. It must be unique within a task.
name

string

A human readable name for the artifact.
description

string

Optional. A human readable description of the artifact.
parts[]

object (Part)

Required. The content of the artifact. Must contain at least one part.
metadata

object (Struct format)

Optional. Metadata included with the artifact.
extensions[]

string

The URIs of extensions that are present or contributed to this Artifact.