An agent runs through a harness that connects to the broker's remote MCP server. The broker registers the agent sub-identity, gives it a dedicated inbox, mints assertions and records ToS acceptances. This section covers the first signup, the identity lifecycle, the inbox, credentials and the ledger.
What you get
- A sub-identity. An id (
agt_...), a display name, a harness label and a set of delegated scopes. - A dedicated inbox. An address of the form
<agent-slug>@agents.agentregistrar.dev, readable by the agent through MCP and by the human in the portal. - Scoped delegation. A new agent starts with
tos:accept,signup:free_tier,inbox:readandinbox:send. - A ledger. One row per ToS acceptance, with the exact terms URL, hash and master agreement version, plus one proof row per provider account.
- A kill switch. A per-agent revocation control in the portal that stops new assertions and further identity and inbox calls for that agent.
Before you start
- A harness that supports remote MCP over OAuth. The support matrix lists each client with its tier, the date it was checked and a page with the exact configuration. No client is tier 1 yet: OpenCode V2 and Claude Code are documented at tier 2, and the rest at tier 2 or 3.
- A GitHub account for the human owner, and a browser for the OAuth step. The OAuth consent is a human action; no tool can complete it for you.
- A terminal, if your client is configured from the command line.
- Nothing else. There is no API key to create and no separate broker signup form.
The path
- Quickstart: from zero to a first brokered signup.
- First signup: the same flow as a tutorial, with every request and response shape.
- Identity lifecycle: register, resume, prove, record, revoke and re-register.
- Inbox and verification: list, read, wait and send, plus one-time codes.
- Credentials and recovery: store the credential at handoff and never re-run signup to recover it.
- ToS and ledger: what was accepted, where it is recorded and who gets the receipt.
- Troubleshooting: OAuth, 401, hash mismatches, inbox timeouts and provider errors.
The endpoint
Every client connects to the same remote MCP server:
https://agentregistrar.dev/mcpThe server publishes OAuth metadata and a JWKS, so a compliant client discovers the authorization server and registers itself. The broker endpoint rejects an unauthenticated request with 401 and a WWW-Authenticate challenge.
Where the reference is
Tool names, inputs, side effects and error codes are listed in the reference section. The protocol rules behind them are in the specification. Shared vocabulary is in Key concepts.
To try the same flows against deployed test providers, start with the demo network.
Providers should read Accept agent signups instead.