Accept agents at your own API

Give the agent a token for your API

In the console, open Integrations > Applications and register your API as an application. Then grant the agent access to the application registered for your API.

The application's client ID is how a token names your API. It is in the header of the application's page, and under "Client ID" in the Overview section.

The agent then asks for an access token for your API, with the client ID as resource:

curl https://acme.authfi.io/apis/regional/v1/ai/auth/token \
  -d grant_type=client_credentials \
  -d client_id=agt_7f3a9c21 \
  -d client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer \
  -d client_assertion="$ASSERTION" \
  -d resource="$API_CLIENT_ID"

$ASSERTION is a fresh client assertion, the short statement the agent signs with its own key. Build it as in Give an AI agent an identity. $API_CLIENT_ID is the client ID of your API's application. agt_7f3a9c21 is the agent ID, shown as "Client id" on the agent's Connect tab under Identity > AI Agents. The same tab shows the token endpoint and a worked example of this request.

{
  "access_token": "eyJhbGciOiJFZERTQSIs…",
  "token_type": "Bearer",
  "expires_in": 900,
  "agent_id": "agt_7f3a9c21",
  "type": "autonomous",
  "capabilities": ["transfer:accounts"]
}

An agent with no grant on your API gets invalid_target. It cannot obtain a token that your API would accept.

Verify the access token

In your service, check every access token before you act on it.

import { createRemoteJWKSet, jwtVerify } from "jose";

const keys = createRemoteJWKSet(new URL("https://acme.authfi.io/.well-known/jwks.json"));

export async function verifyAgent(token) {
  const { payload } = await jwtVerify(token, keys, {
    issuer: "https://acme.authfi.io",
    audience: process.env.API_CLIENT_ID,
    algorithms: ["EdDSA"],
    typ: "at+jwt",
  });
  return payload;
}

Both libraries cache the key set and fetch it again when they meet a kid they do not know. That is what key rotation needs.

Read who is calling

The verified claims tell you which agent is calling and who is accountable for it.

An agent calls either as itself or for a person. To tell the two cases apart, look for act.

A token with act is issued after the person approves the agent's request.

Decide what the caller may do from capabilities, and record client_id with everything it does.

Check the action the agent is bound to

For a sensitive action, require a transaction token as well as the access token. A transaction token names one action and its details, and lasts 60 seconds.

{
  "typ": "txn_token+jwt",
  "sub": "agt_7f3a9c21",
  "txn": "0b7d6a52-…",
  "azd": {
    "action": "transfer:accounts",
    "resource": "account:4821",
    "context": { "amount": 1200, "currency": "USD", "account_type": "business" }
  }
}

Compare azd with what the request asks for. A token issued for 1,200 must not carry a request for 12,000. Reject the request if anything differs.