A developer-friendly API helps consumers find the right operation, understand its contract, implement it predictably, recover from failures, and keep working as the service changes. Use the checklist below to review an API from a client developer’s point of view—not just from the perspective of the team building it.
1. Does the API start from real consumer tasks?
Begin with the jobs consumers need to complete, the roles that perform them, and the permissions those jobs require. Use those scenarios to shape resources, relationships, and operations. Avoid exposing internal database tables or service boundaries simply because they exist; the customer-facing model should make the consumer’s work straightforward.
Microsoft Graph’s REST API guidelines call for an API-first approach: define the user-facing interface contract before implementation. The guidelines describe the goal as APIs that are “easy to discover, simple to use, fit for purpose, and consistent across your products.” Microsoft Graph REST API Guidelines
- Can you name the consumer scenarios and roles the API supports?
- Do the resources and operations map to those tasks rather than internal implementation details?
- Are the required permissions clear for each task?
2. Can consumers discover and understand the API surface?
Use familiar HTTP, REST, and JSON conventions where they suit the API, and make names specific enough to communicate purpose. Keep terminology and behavior consistent across endpoints. Avoid invented jargon, vague labels, and multiple synonyms for the same concept; each makes it harder for consumers to predict what an operation does.
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Consistency does not mean choosing one naming convention as a universal rule. It means choosing conventions deliberately and applying them predictably, with relationships among resources and abstractions made clear. Microsoft’s Azure API design guidance discusses naming and consistency as part of designing services for consumers. Azure API design best practices
3. Is the API contract complete and usable?
Consumers need to know what to send, what they will receive, and what conditions affect an operation. Document request and response shapes, required fields, authentication, permissions, operation behavior, and errors. Include examples that reflect realistic requests and responses rather than only a minimal happy path.
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A machine-readable description can help generate documentation and SDKs and let consumers work against an agreed interface while service implementation is still in progress. OpenAPI is one option in Microsoft’s general web API guidance, not the only valid format. Whatever format you choose, keep it aligned with actual service behavior: a polished contract that disagrees with the running API creates confusion rather than reducing it. Microsoft Azure API design best practices
- Can a developer identify authentication and authorization requirements before calling an endpoint?
- Are required and optional fields, response shapes, and operation effects specified?
- Can consumers use the contract or examples to try the API before implementation is complete?
4. Do errors help clients recover?
Return appropriate HTTP status codes and stable, machine-readable error codes so client software can distinguish conditions and respond appropriately. Pair them with precise messages that explain what the caller can change or do next. Include a request identifier that support and operations teams can use to locate a request in service logs, while avoiding sensitive information in responses.
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Microsoft’s Azure service design guidance says, “The errors returned by your service are a critical part of your developer experience and are part of your API contract.” It also treats changes to status codes and top-level error codes as compatibility-sensitive: clients may depend on them, so changing their meaning can break integrations. Azure API implementation best practices
- Can software distinguish error cases without parsing a human-readable message?
- Does the message identify a useful corrective action without revealing sensitive details?
- Can a support team trace a customer’s report using the request identifier?
5. Will collections remain manageable as they grow?
For collections or responses that may become large, plan filtering and pagination as part of the API design. Pagination limits response size and lets a client retrieve results in manageable pieces. Azure guidance warns that adding pagination later can be a breaking change, so consider it before general availability when growth is plausible.
That guidance recommends server-driven paging in most cases: the service controls page boundaries and returns an opaque next-page link, which clients follow rather than reconstructing pagination state. Client control over page size can still be useful when appropriate; weigh that flexibility against server protection and bounded payloads. Azure API implementation best practices
- Could the collection grow enough that a single response becomes unwieldy?
- Can clients continue safely using a returned next-page link?
- Would filtering or page-size controls help without allowing requests that overwhelm the service?
6. Can the API evolve without silently breaking clients?
Prefer changes that preserve existing client behavior. When a breaking change is necessary, communicate it clearly and give consumers a deliberate migration path. Decide on versioning before launch by comparing client clarity, compatibility expectations, URI stability, caching, link behavior, routing complexity, and the cost of supporting multiple versions.
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Microsoft’s architecture guidance covers URI, query-string, header, and media-type versioning, with different implications for routing, caching, and links. It does not establish one universally best mechanism; the right choice depends on the API’s consumers and operating constraints. Azure API design best practices
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.7. Can consumers implement it with their tools and languages?
Consider how the API will work for developers using different programming languages and tooling. SDKs can make common tasks easier, but they should reflect the same stable contract and behavior as the underlying API. Validate more than a successful request: realistic workflows should include permission failures, actionable errors, and recovery paths.
Microsoft Graph and Azure offer product-specific recommendations, not universal prescriptions for every API. The broader test is whether consumers can discover the contract, implement the intended tasks, diagnose problems, and upgrade safely with the tools they use.
Quick Recap
A practical review pass
- List consumer scenarios: Identify important tasks, roles, and required permissions.
- Walk the surface: Check whether resource names, relationships, and operation behavior are specific and consistent.
- Read the contract as a new consumer: Verify request and response shapes, authentication, permissions, errors, and examples.
- Exercise failure and scale cases: Check permission errors, recoverable failures, and large collections or payloads.
- Review the change path: Confirm that compatibility expectations and versioning decisions are understandable before consumers depend on the API.
- Try more than the happy path: Validate realistic workflows with the intended SDKs, languages, and tooling.
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