Answer Through a Remote A2A Agent (A2A Solver)¶

The A2A solver makes an OVOS persona hand each question to an agent on another server, over the A2A protocol. Use the A2A solver when OVOS must use an agent that speaks A2A as the brain of a persona, for example an agent built with LangGraph, CrewAI or Google ADK. A voice question then gets the answer of the remote agent.

What you get¶

The persona handler ovos-a2a-solver from the ovos-a2a-solver-plugin package. It sends each user message to the remote agent and returns the reply as the answer of the persona.

Steps¶

Install the plugin:

pip install --pre ovos-a2a-solver-plugin

Write the persona file. agent_url is the base URL of the remote agent:

{
  "name": "remote-helper",
  "handlers": ["ovos-a2a-solver"],
  "ovos-a2a-solver": {
    "agent_url": "https://my-a2a-agent.example.com",
    "auth_header": "Bearer <token>",
    "timeout": 60,
    "streaming": false
  }
}

Key	Default	Description
`agent_url`	none	Base URL of the A2A agent. Required.
`auth_header`	none	The value of the `Authorization` header, for example `Bearer <token>`.
`timeout`	`60`	Seconds for each call.
`streaming`	`false`	Use the streaming call of the agent.

Which agents it can reach¶

The plugin uses the a2a-sdk client. It reads the agent card from /.well-known/agent-card.json under agent_url, and it uses the transport that the card names. It speaks A2A 1.0 and A2A 0.3. An agent that publishes only /.well-known/agent.json, the path of A2A 0.2, is not supported.

The OVOS persona server from Talk to an OVOS persona over A2A is a valid remote agent. Set agent_url to the value of its --a2a-base-url flag, for example http://localhost:8337/a2a. A persona that sent "what is the speed of light?" to a persona server with a RiveScript persona gave this answer:

Are such questions much on your mind?

The plugin sends only the newest user message. The remote agent keeps the conversation for each OVOS session.

If it fails¶

The persona speaks one line of its error dialog when the remote agent cannot answer. The log line that starts with A2AChatEngine: task failed gives the cause.

What you see in the log	Cause	What to do
`Network communication error fetching agent card`	The agent is not running, or `agent_url` is wrong	Make sure that `<agent_url>/.well-known/agent-card.json` answers.
`Client Request timed out`	The agent took longer than `timeout`	Increase `timeout`.
`A2A task ended in TASK_STATE_FAILED`	The agent failed the task	Read the log of the agent.

More information¶

Configuration in the ovos-a2a-agent-plugin README.
Personas for persona files and handlers.
The A2A specification.