Connect a custom A2A-protocol agent to Google Antigravity — 3 steps.

connecting-antigravity-to-an-a2a-agent.md

Connecting Google Antigravity to a custom A2A agent

Quick setup for registering a custom A2A-protocol (v0.3.0) agent in Antigravity so you can invoke it with @<agent-name>.

What you need

• A running A2A agent that serves its agentcard at <your-agent-base-url>/.well-known/agent-card.json and accepts JSON-RPC message/send at its root.
• Google Antigravity installed and signed in, with a project opened.

1. Drop a registration file in the project

Create .gemini/agents/<your-agent>.md at your project root. The filename slug becomes the @<your-agent> handle in Antigravity. A short description and the URL are enough:

# <Your Agent Name>

What it does, in one or two sentences.

Reach it at: https://<your-agent-host>/api/<your-agent>/

2. Restart Antigravity

Fully quit and relaunch — that's the most reliable way to make Antigravity re-scan its startup files and pick up the new agent. /agents reload from the chat composer also seems to work but is less reliable; if /agents list still doesn't show your agent after a reload, just restart.

3. Confirm + invoke

In an Antigravity chat:

• /agents list — your agent should appear in the list.
• @<your-agent> <question> — invokes it. Example: @my-agent What's the weather in Brooklyn?

That's it.