Integrate an agent with DMC-12

This is the how-to companion to the dmc-12.ai overview and the machine-readable spec at dmc12.ai. It walks a partner agent — a buyer agent, a marketplace, a broker, or an OEM agent — from discovery to a completed deal hand-off against a deployment of the UCP Merchant Binding. This guide is static documentation: worked examples use the spec's fictional merchant (Aurora Motors Group), and real endpoints always come from a merchant's published /.well-known/ucp.

1. The lifecycle

Every transaction-class flow is the same four steps. Reads (inventory, pricing disclosure) can happen at any point.

Quotes and reservations both carry a 30-minute TTL, so an agent should run the quote → reserve → hand-off tail back-to-back once the buyer has committed. The deep-dive pages cover each step: Inventory → Quotes → Reservations → Deal hand-off.

2. Pick a rail: A2A or MCP

The same DMC-12 capabilities are served over two wires from one Cloud Run service. Choose by who your caller is.

This guide uses the A2A rail for every worked example — it is the path partners integrate against. The wire envelope is a standard JSON-RPC tools/call:

POST /a2a/   Authorization: Bearer <token>

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "search_inventory",
    "arguments": { "query": "2024 Outback AWD under 35k", "limit": 5 }
  }
}

And tools/list (no params) returns the deployment's scope-filtered tool catalog. Every response is wrapped in a standard envelope:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "data": { /* the tool payload */ },
    "_metadata": {
      "trace_id": "trc_…",   // log this — it correlates to the audit row
      "tool": "search_inventory",
      "agent_id": "…@clients",
      "protocol": "a2a",
      "timestamp": "2026-05-27T18:04:11+00:00"
    }
  }
}

3. Discovery — check the well-knowns

Every claim a deployment makes is backed by an unauthenticated, cacheable document at a canonical URL. Fetch these first; they are the source of truth for tool count, capability versions, scopes, and the auth server.

What each one returns, in brief:

4. Auth, in one paragraph

Partners authenticate with OAuth 2.1 client-credentials against the deployment's authorization server — its issuer and audience come from the deployment's RFC 9728 protected-resource metadata, never from documentation. Mint an access token, cache it for most of its TTL, and send it as a Bearer token on every /a2a/ call. Your effective permissions are the intersection of the scopes the deployment seeded for your agent and the scopes in your token. Onboarding is deployment-specific — see Deployment onboarding for the pattern (credential bundle, mint command, rate limits, scope matrix).

5. Data formats

Every DMC-12 field follows one of these conventions. The per-capability pages (Inventory, Quotes, Reservations, Deal hand-off) link back here rather than restating them. All enum values are lower-case and case-sensitive — available, not Available.