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An A2A connection links your Callers agent to an external AI agent that supports the open Agent2Agent (A2A) protocol. During a conversation, Callers sends the conversation to the external agent, and the external agent’s replies guide what your Callers agent says and does. Use it when the reasoning or data lives in an agent you already run, such as a support agent with access to your back office, and you want Callers to handle the voice or chat side.

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Requirements

Your external agent must:
  • Expose an A2A agent card at its base URL. Callers reads the card to get the agent’s name, endpoint, and optional input schema.
  • Accept A2A requests over JSON-RPC.
  • Accept a bearer token. Callers sends Authorization: Bearer <token> with every request, including the agent card request.
  • Be reachable over the public internet. Requests come from Callers’ outbound IP addresses, 35.245.204.86 and 35.221.61.75.

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Create a connection

1

Open A2A Connections

In the left sidebar, under Resources, click A2A Connections, then Create New.
2

Enter the URL and token

Enter the agent’s base URL and the authentication Token. Callers fetches the agent card when you save. The agent’s name comes from the card.
3

Adjust additional settings (optional)

Expand Additional settings to change how and when Callers talks to the agent. See the settings table below.
4

Save

The connection appears in the list with the agents that use it (Used by) and its creation date.

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Connection settings

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Add a connection to an agent

1

Open the agent's scenarios

In the agent editor, open Scenarios. Click Connect A2A in the header.
2

Select connections

Select one or more A2A connections. The button changes to A2A Connected with the number of connections.
3

Map metadata (optional)

Click the edit icon next to a connection to open Edit mapping. If the agent card defines an input schema, map each field to an agent variable or a fixed value, so the external agent receives structured context with each request. JSON values can include {{variable}} placeholders. You can also set a Context ID from a contact variable to group conversations on the external agent’s side.
4

Save and test

Save the agent and place a test call. A2A requests and responses appear in the transcript.
Metadata mappings support contact variables only. Call data, metadata, and action tags aren’t supported in mappings.

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Wait for the external agent in the script

By default the conversation keeps flowing while the external agent works. To hold the script until it answers, add a Wait for results step and choose the connection under Wait for (as a Connected agent). A Wait for results step must be the only step in its block. If the list is empty, the message “Enable an A2A connection for this agent first.” means you need to connect the agent on the Scenarios page first.

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Manage connections

  • Edit: open the connection from the list to change the URL, token, or settings. Changes apply to every agent that uses it.
  • Delete: removes the connection permanently and from every agent that uses it. Check Used by first.

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Best practices

  • Keep the external agent fast. It’s part of a live conversation. Return short, direct guidance and avoid long tool chains on the critical path.
  • Start with On user messages. It sends fewer requests and gives the external agent complete turns. Switch to On every message only if the external agent needs to react to your agent’s own replies in real time.
  • Pass identifiers as metadata, such as a customer ID, instead of relying on the external agent to parse them from speech.
  • Use a Wait for results step with a fallback where the conversation can’t continue without the external agent’s answer.

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Troubleshooting

Callers couldn’t fetch the agent card. Check that the base URL is correct and public, that the agent card is published, and that the token is valid.
The agent card doesn’t define an input schema, or Sync input schema from agent card was off when you saved. Turn it on and save the connection again.
Check that the connection is selected on the agent’s Scenarios page and that the external agent returns a response before the turn ends. Use a Wait for results step if the answer is required.
Turn off Restart response when new A2A input arrives, reduce the external agent’s latency, and send requests On user messages.

Scenarios

Where you connect A2A agents to an agent.

Steps

The Wait for results step and other step types.

Actions overview

Other ways to call your systems during a conversation.

Variables

Values you can map into A2A metadata.