magnus919_agent-skills/api-design-and-evolution/references/contract-verification.md

Contract Verification

Validate an interface at multiple boundaries. A schema linter, generated document, or passing mock is useful evidence but is not integration proof.

Boundary	Evidence to collect
Contract	Schema parse/validation, references, examples, negative examples, documented semantics
Provider	Conformance tests for success, errors, authorization, limits, concurrency, and side effects
Consumer	Consumer expectations, generated-client behavior, tolerant/strict parsing, migration fixtures
Compatibility	Consumer-aware diff, enum/default/null/order/pagination and behavioral regression assessment
Deployed	Authenticated end-to-end test against the intended deployment, telemetry and rollback evidence

For an event or webhook interface, test the stated publisher/subscriber perspective, envelope, signature profile, duplicate/reorder/gap behavior, and delivery failure handling. For a stream, test reconnect and checkpoint/loss semantics.

Deployed-Boundary Verification

Use the contract-review template to record evidence, gaps, owners, and a verdict. Load verification-methodology when a formal evidence-backed completion assessment is needed, and spec-driven-development when contracts must be connected to delivery specifications and acceptance gates.