Complete a task across several services.
An agent checks inventory in a partner organization and reads an approved quote. Six parts show sign-in, delegation, policy checks, restricted tokens, results and renewal.
Why this lesson?
An agent checks a partner’s inventory and asks a worker to read an approved quote. Each service checks the permissions needed for its part of the task.
Learning goal and prerequisites
Find the protected tool
The user asks the agent to check order 1042 and read its quote. The host finds the Model Context Protocol (MCP) resource and its authorization server. This example assumes client registration is already complete and summarizes some metadata requests.
Inspect request, response, and claims
Try a failure scenario
↳ Change a condition
Read the detailed explanation
Why it exists, how it works, and where it fits
Real systems rarely use only one authentication or authorization control. A user may sign in and a host may obtain an access token. One service may exchange that token for another audience. Workloads may authenticate to each other, and a downstream worker may receive an even narrower delegated capability. The security comes from how those controls fit together.
The capstone follows one read-only task across several trust boundaries. At each boundary, the receiving component asks a few specific questions. Who is calling? Which credential proves that identity? Was the credential meant for this service? What action is being requested? What permission or relationship allows that action?
When the request moves to another service or organization, the system should avoid carrying one broad credential everywhere. Instead, it uses a credential appropriate for the next resource and preserves the identities of the user and acting service where needed. Downstream delegation can narrow authority again before another worker receives it.
No single protocol provides the whole security model. Authentication, token validation, audience checks, workload identity, authorization policy, delegation limits, and lifecycle controls each solve a different problem. The purpose of the capstone is to make those connections visible so the learner can recognize which control belongs at each boundary.
Investigation
Inspect the traffic, select a diagnosis in the checkpoint, then reveal the repair.
Check your understanding
Pass the lesson quiz
Answer every question correctly to unlock the next lesson. Retry as often as you need.