Building Custom Agents in Antigravity: Beyond the Defaults

Antigravity ships with great default agents: Builder, Tester, Explainer.
But every team is different. Maybe you need a “Security Auditor” or a “Tailwind CSS Expert”.

Here is how to build your own Custom Agents.

The Agent Definition File

Agents are defined in `.antigravity/agents.yaml`.

“`yaml
agents:
– name: “Security Auditor”
role: “Analyze code for security vulnerabilities”
model: “gemini-3-pro-security”
tools:
– “terminal”
– “file_read”
instructions: |
You are a paranoid security expert.
Always check for SQL injection, XSS, and CSRF.
When you find a vulnerability, cite the OWASP Top 10.
Do not fix the code, only report it.
“`

Adding Custom Tools

You can give agents custom tools by writing Python scripts.

Example: A “Slack Notifier” Tool

1. Create `tools/notify_slack.py`.
2. Register it in `agents.yaml`:

“`yaml
tools:
– name: “notify_slack”
command: “python tools/notify_slack.py {message}”
“`

Now your agent can say:
> “I found a critical bug. Notifying the team on Slack.”

Sharing Agents

You can share your agents with your team.
Commit the `.antigravity` folder to Git. Now, everyone who clones the repo gets your custom “Security Auditor” agent.

Use Case: The “Compliance Agent”

At BYS Marketing, we built a “GDPR Compliance Agent”.
* Role: Scans every PR.
* Instruction: “Check if any PII (Personally Identifiable Information) is being logged to the console or sent to non-compliant APIs.”

It saves us from costly legal mistakes.

Conclusion

Custom Agents allow you to codify your team's best practices into active participants in the development process. You aren't just hiring developers; you are building digital colleagues.

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Need custom AI agents for your workflow?
Contact BYS Marketing. We build bespoke agent architectures for enterprise teams.