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User ManualNeed configuration, code or deployment details? In the Technical Manual: Agent-to-Agent Protocol (A2A)A2A HostA2A Client Integration

Agents and Agent-to-Agent (A2A)

Some jobs are best done by a specialist. An Agent is an AI profile with one job, its own instructions and its own tools. Another assistant hands a job to it and uses its answer. The Agent-to-Agent (A2A) protocol lets agents on different systems find each other and work together: your site can offer its agents to other systems, and your assistants can call the agents of other systems.

MenuArtificial Intelligence > Profiles (create agents, and choose them on the Capabilities tab); Artificial Intelligence > Agent to Agent Hosts
PermissionManage AI profiles; Manage Agent-to-Agent Connections; Access the A2A Host (for callers of your agents)
FeatureAgent-to-Agent (A2A) Client; Agent-to-Agent (A2A) Host
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What you see depends on your role. If the menu, a button or a setting on this page is missing, ask your administrator to give you the permission listed above or to turn on the feature. Only administrators can turn features on and change site settings.

The video covers why specialist agents help, how Agent profiles, the A2A Host and the A2A Client fit together, and each task below.

Each part is its own feature, so you only see the menus of the features that are turned on: Agent to Agent Hosts comes with the A2A Client.

Create an agent​

  1. Open Artificial Intelligence > Profiles and click Add Profile.
  2. In the New AI Profile window, click Start on Blank profile. The other cards are ready-made profiles, including agents you can start from.
  3. Enter a Title, and set the Profile type to Agent. The Description and Availability appear.
  4. Write the Description for the other assistants. It says exactly what the agent does and when to call it, and it is how they decide.
  5. Choose the Availability:
    • On demand: the agent is only included when it fits the request.
    • Always available: the agent is included in every AI request. This uses more tokens and costs more; use it only for agents every assistant must be able to reach.
  6. Under System instructions, tell the agent how to behave, and click Save.

To try an agent on its own, use Invoke Profile from its Actions menu (see Chat with an AI assistant).

Offer your agents to other systems​

With the Agent-to-Agent (A2A) Host feature on, your site offers every Agent profile to other systems, which discover them in the site's agent card, at /.well-known/agent-card.json, and send them messages to the single A2A address of the site, /a2a. Your technical team chooses how callers sign in (no sign-in for testing, an API key, or OpenID Connect). When the host asks for it, a caller also needs the Access the A2A Host permission. See the Technical Manual.

Connect to another system​

  1. Open Artificial Intelligence > Agent to Agent Hosts and click Add Connection.
  2. Enter a Title and the Endpoint, the address of the other system's A2A host. The host of a CrestApps site answers at the site's address followed by /a2a.
  3. Choose the Authentication. The options are the same as for an MCP connection: Anonymous (No Authentication), API Key, Basic Authentication, three OAuth 2.0 options and Custom Headers (Advanced). Anonymous suits an open host or a test.
  4. Click Save.

The site reads the agent card of the host when an assistant first uses the connection, so a wrong address shows up the first time an assistant calls the agent. The list shows each connection with its endpoint.

Give an assistant the agents​

  1. Open Artificial Intelligence > Profiles, edit the profile of the assistant, and open the Capabilities tab.
  2. Under A2A Connections, tick the connection. Each agent that the host offers becomes something the assistant can call.
  3. Under Agents, tick the agents of this site that the assistant may call. Always-available agents are already included, and the tab says how many there are.
  4. Click Save.

Profile templates and chat interactions have the same lists.

Then ask the assistant something for the specialist. It hands the question to the agent and answers with what the agent returned.

Use cases​

  • Specialists. A legal, finance or warranty agent that answers in its own area, with its own instructions.
  • Partners. A supplier or a sister company offers an agent, and your assistants call it.
  • Reuse. One agent serves many assistants, so you keep its instructions in one place.
  • Care. Describe each agent precisely, and give an assistant only the agents it needs.