# Patterns

Worked deployment patterns that trace real-world agent topologies through the spec end-to-end. Each pattern cites specific section numbers — [§1.1](/protocol/trust.md#11-passport-verification-procedure) verification, [§1.2](/protocol/trust.md#12-presentation-proof) presentation proof, [§10.3.3](/spec/next#1033-credential-schemes) credential schemes, [§10.4](/spec/next#104-authorization-scopes) authorization scopes — so an implementer reading along can move from "I want this behavior in production" to "the normative paragraph that says how" in one lookup.

This section is **non-normative**. The normative content lives in the [specification](/spec/next). Patterns illustrate composition, document failure modes, and provide regulators or auditors with reconstructable end-to-end traces — but if a pattern ever conflicts with the spec, the spec wins.

## What belongs here[​](#what-belongs-here "Direct link to What belongs here")

* **Multi-hop scenarios** that exercise the cohesive Authentication structure ([§10.3](/spec/next#103-authentication)) and Authorization Scopes ([§10.4](/spec/next#104-authorization-scopes)) across both the human/external boundary ([§10.3.3](/spec/next#1033-credential-schemes) OAuth 2.1) and the agent-to-agent boundary ([§1.1](/protocol/trust.md#11-passport-verification-procedure) + [§1.2](/protocol/trust.md#12-presentation-proof)).
* **Real-world deployment shapes** with concrete actors, scopes, audit chains, and failure modes — not abstract "Alice and Bob" pedagogy.
* **Cross-flow composition** where the [§2.3](/protocol/trust.md#23-composition-across-boundaries-multi-hop-authorization) independent-vs-reduction patterns become operationally visible.

## What does not belong here[​](#what-does-not-belong-here "Direct link to What does not belong here")

* **Standalone ADL document samples** — those go in [Examples](/spec/next/examples) (e.g. `minimal.yaml`, `production.yaml`).
* **Test vectors** — those go in `core/_next/test-vectors/`, with their own SCHEMA.md and conformance runners.
* **Implementer guides** that prescribe "do these steps to build X" — patterns describe how the spec composes, not how to build something.

## Index[​](#index "Direct link to Index")

| Pattern                                                                            | Illustrated by                                                                                                                                             | Authentication paths                                                                        | Authorization patterns                                                                                                                   |
| ---------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| [Multi-hop authentication and authorization](/patterns/multi-hop-authorization.md) | Vacation-booking scenario: human → assistant → MCP calendar / travel discovery / flight + hotel agents                                                     | OAuth 2.1, OAuth Token Exchange, ADL passport + presentation proof                          | Scope reduction across hops, escalated scopes for booking, sender-constrained `proof.scopes`                                             |
| [Exposing agents to external callers](/patterns/exposing-agents.md)                | Fortune-50 brokerage scenario: human client website chat + well-known discovery for peer agents                                                            | OIDC per session, ADL passport + presentation proof per request                             | Entitlements as scopes, provider allowlist + attestation, classification gating, step-up for high-stakes                                 |
| [Verifying inbound callers (the PEP)](/patterns/inbound-verification.md)           | One Policy Enforcement Point across host shapes — agent-runtime plugin, AI-aware gateway, dedicated ADL verifier, and (incidentally) a generic API gateway | OIDC (human path) + ADL passport/proof (agent path) at one PEP                              | Ceiling + route-required scopes, principal/delegation enforcement, classification gating, verification boundary vs internal trust domain |
| [Mediating agent egress through an AI gateway](/patterns/ai-gateway.md)            | Support-agent platform behind an AI gateway (Kong AI / Cloudflare / Portkey / LiteLLM): model + tool + agent-to-agent egress                               | Gateway custodies the agent key, constructs passport + proof + delegation per outbound call | Key custody, per-call tool/MCP credentialing, budget + classification enforcement, model routing vs declared model                       |

## Conventions[​](#conventions "Direct link to Conventions")

* **One pattern per file**, named after the capability it demonstrates.
* **Section anchors** at the end of every pattern mapping every operation to the exact `§10.x.y.z` it cites.
* **Failure modes section** documenting what happens when each authentication or authorization gate rejects.
* **End-to-end audit reconstruction** showing how the chain reconstructs across hops where no single hop sees the full picture.
* **Unversioned living guidance**: patterns are non-normative and track the current spec; they are not snapshotted per release.