Make outcomes explicit
A boolean alone can be ambiguous. Define verified, rejected, expired, unavailable, and malformed outcomes with stable meanings. Treat missing results as failures unless an explicit policy states otherwise.
Publish example payloads and error semantics for each supported outcome.
Authenticate requests
The service boundary must distinguish approved callers and limit what each integration can do. Never put secret integration credentials in browser JavaScript.
Keep credentials server-side and rotate them through a documented process.
Keep verification server-side
The browser can collect a challenge response, but the final authorization decision belongs to the application server. Client-side UI changes are not security boundaries.
Verify results and enforce action permissions in the same backend trust boundary.
Use short validity windows
Proofs should expire and be scoped. Carefully consider one-time consumption, timestamp skew, replay protection, and retries.
Exercise multiple retries and concurrent requests in integration tests.
Treat errors as product features
A legitimate integrator needs to know what to retry, what to correct, and what not to trust. Consistent HTTP semantics and documentation reduce failure rates.
Maintain contract tests and publish a versioning and deprecation policy.
An API contract is a shared vocabulary
A reliable contract should tell integrators which values are authoritative and which are merely informational. For example, a field called “verified” is not sufficient if no one knows whether it refers to human participation, account authentication, or document identity verification. Define each outcome, who issued it, its scope, its freshness, and how a relying application should interpret it. Include explicit examples for successful and unsuccessful flows.
Write the contract before building SDK conveniences. The SDK should make correct usage easy without concealing security-relevant semantics. Document the difference between “participant did not complete the check,” “result expired,” “verification service unavailable,” and “client request malformed.” Distinct causes lead to different recovery actions. Clear contracts reduce the chance that integrators will accidentally treat every non-error response as authorization.
Create a short glossary for every field and a decision table showing whether each result may authorize an action.
Idempotency and retry semantics matter
Distributed calls fail in ambiguous ways. A client may not know whether a request was accepted when the connection drops. It may retry, creating duplicate attempts or repeated billing events unless the service supports idempotent operations. A challenge issuance endpoint should document whether repeating a request returns the same challenge or creates a new one. A result consumption endpoint should make duplicate submissions safe and predictable.
Do not assume HTTP 200 means a protected action succeeded. The verification result and the business operation are separate events, each with its own state. Expose a stable correlation identifier for troubleshooting without revealing private input data. Use bounded retry strategies, explicit timeouts, and clear rules for which errors are transient. Test the contract under network interruption and concurrent clients rather than only with clean local requests.
Write retry behavior for challenge creation, verification, and consumption as three separate operations.
Operational security is an API feature
Credentials need scope, storage rules, rotation, and revocation. Secrets should never be bundled into browser code or pasted into public documentation. Logging should capture structured outcome codes and minimal debugging identifiers, while avoiding complete verification payloads and personal attributes. Limits should be designed at the tenant and endpoint level, with fair use and predictable error responses.
Document versioning from the outset. If a response field changes meaning, integrators need a migration path and a clear deadline. Provide a test environment that cannot be confused with a production attestation service; simulated outcomes should be visibly labeled and isolated. Good developer experience includes honest limitations, stable examples, and a path to get help when something fails.
Review credentials, log payloads, versioning, and test-environment boundaries in the same release checklist as endpoint behavior.
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