What Is Arbiter?

Arbiter is a policy firewall for AI agents that need access to sensitive services. It runs in your trusted environment, keeps upstream account credentials inside the deployment, and exposes only the actions an operator has configured and approved.

Arbiter is built as a small module system with one plugin per service. The SMTP and IMAP plugins can restrict who an agent may email, which messages it may read from configured folders, and other service-specific behavior. Agents get a narrow, discoverable surface through the arbiter CLI instead of raw service access.

The shape

• The server composes config, loads plugins, exposes the Arbiter client interface, and enforces the shared discovery flow.
• Operators configure accounts, credentials, service activation, and policies.
• Agents discover capabilities before selecting operations.
• Service plugins own their schemas, bootstrap templates, policy checks, and runtime behavior.

Current capabilities

• SMTP service plugin.
• IMAP service plugin.

Where to start

• New operator: start with Quickstart.
• Docker deployment operator: install Reploy and follow Docker Deployment.
• Agent/tool user: start with Arbiter CLI Reference.
• Plugin author: start with Writing Plugins.