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Before approving an API contract, check that intended consumers can understand it, each operation defines requests and outcomes, compatibility and deprecation are clear, security boundaries are reviewable, and there is evidence the running API will conform. A valid specification file is not enough: approval should be based on an explicit contract and a plan to keep implementation and tests aligned with it.
1. Can intended consumers understand and use the API?
Begin with the developers and systems that will call the API and the tasks they need to complete. GOV.UK guidance recommends understanding user needs before building an API and notes that ease of understanding affects whether people use it. A design-stage specification gives consumers something concrete to review while changes are still relatively easy to make.
Check whether operation names, resource boundaries, terminology, and examples make the intended use clear. Ask reviewers to identify any assumptions they would otherwise have to learn from undocumented conversations or by inspecting implementation. An example can illustrate a contract, but it should not be the only place where required behavior is defined.
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2. Are requests, responses, and failures explicit?
Review every operation, not just the happy-path example. Confirm that a consumer can determine what to send, what the service may return, and what failure means.
- Inputs: Check parameters and request bodies, required versus optional fields, accepted values, data constraints, and input-validation expectations.
- Success outcomes: Confirm the documented response shape and status codes, including which outcomes an operation can produce.
- Failure outcomes: Check that errors and status codes distinguish meaningful cases, such as invalid input from lack of access.
Home Office API guidance calls for appropriate status codes and input validation; its example uses 403 to communicate that access is not permitted. Do not infer unspecified behavior from a sample payload or an implementation guess. If a consumer needs to know whether a field can be omitted, what values are accepted, or how a failure is represented, that behavior belongs in the contract. See the Home Office standard for designing and maintaining an API.
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3. Are compatibility and lifecycle expectations clear?
An API contract affects existing consumers as well as new ones. Look for a stated versioning policy, a definition of breaking change, how deprecation will be announced, how long older versions will be supported, and what migration path consumers have when they are affected.
GOV.UK advises avoiding changes that stop older versions working where possible; when an older version cannot be maintained, a new URI version is one option. Home Office guidance recommends choosing a versioning strategy and communicating deprecation to consumers. It names URI-path, query-parameter, and header approaches. These sources do not establish one versioning style as correct for every API, so the contract should explain the choice and its consequences rather than assume consumers will know the policy.
When assessing a proposed approach, consider how easily clients can identify the version, whether versioning applies to an endpoint or the API more broadly, the migration burden, deprecation communication and support, and the operational cost of maintaining older versions. GOV.UK describes URI versioning as simple and commonly used, not mandatory. The policy should make it possible for consumers to plan for change.
4. Can reviewers see the security boundaries?
Check the contract and its supporting design for authentication and authorization requirements, least-privilege access, sensitive operations, access to individual records, input validation, and relevant resource controls. Security review should consider data, application, and network access as well as auditing; GOV.UK recommends considering security from the start of API design.
The Western Australia API design decision record (ADR) recommends risk-based authentication and authorization, input validation, rate or resource controls, logging, and additional safeguards for administrative operations. Use those areas to focus review on the API’s actual exposure and risks, rather than treating a generic security declaration as sufficient.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteA written contract is review evidence, not proof that runtime enforcement works. For each important boundary, ask how the behavior will be tested—for example, how unauthorized access is rejected or how a sensitive administrative operation is protected. Increase review depth to match data sensitivity and operational risk. Western Australia ADR-013 sets out the cited security and testing recommendations.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.5. Is there evidence the shipped API will match the contract?
Ask how the contract is version-controlled, validated, and checked against the implementation. The approval package should identify the contract version under review, show relevant test evidence, and explain how changes—especially breaking changes—will be communicated to consumers.
The Western Australia ADR recommends automated contract-conformance, behavior, and security testing in CI/CD, with coverage of material operations and risks. It also recommends reviewing generated or maintained contracts for drift. Look for a process that catches a mismatch between the approved description and the API that is actually shipped, not only a check that the specification file parses successfully.
- Request validation results for the contract version being approved.
- Ask how tests cover representative operations, expected behavior, and relevant security risks.
- Confirm how contract changes and implementation changes are reviewed together and how consumers are notified of breaking changes.
OpenAPI is intended for HTTP API descriptions. Other interface types may need a protocol-native schema or contract; the Western Australia ADR’s OpenAPI-specific requirement excludes non-HTTP protocols, event streams, GraphQL schemas, and unchangeable third-party APIs. Choose a contract and evidence appropriate to the interface rather than forcing an HTTP specification onto a different protocol. ADR-013 describes the scope of its OpenAPI requirement. These government engineering recommendations are guidance, not universal regulatory mandates.
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What to request before approval
Use the review to resolve uncertainty, not merely to collect sign-offs. If any answer is missing, record the gap and ask the owner to provide the relevant contract detail or evidence before approval.
- A specification and examples that intended consumers can interpret without undocumented assumptions.
- Explicit request, response, validation, and error behavior for each operation.
- A versioning and lifecycle policy that covers breaking changes, deprecation, support, and migration.
- Reviewable authentication, authorization, validation, and resource-control expectations, with a way to verify enforcement.
- The contract version, validation and test evidence, and a process for detecting drift and communicating changes.
The five checks apply the consumer-needs emphasis in GOV.UK guidance on API technical and data standards, the Home Office API standard, the OpenAPI specification, and Western Australia ADR-013. Together, they support a defensible decision: approve only when the contract is understandable, behavior and lifecycle are explicit, security boundaries can be assessed, and evidence exists to keep the shipped API aligned with what consumers were promised.
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