Interface Specifications

Interface Specifications define the contract between two software components — what one side can ask for and what the other promises to return — independent of how either side is implemented. They describe the endpoints, methods, data formats, protocols, and error behavior that let systems built by different teams, in different languages, integrate against a stable agreement rather than against each other’s internals.

• A machine-readable contract - A precise description of operations, parameters, and payloads that both producers and consumers can build against.
• Implementation independence - The specification pins the boundary, not the code behind it, so either side can change internally without breaking the other.
• Formats and protocols - Explicit definitions of request/response shapes, media types, and transport so integrations do not rely on guesswork.
• A shared source of truth - One artifact that documentation, client SDKs, mocks, and contract tests can all be generated from.

In modern API operations, interface specifications show up concretely as OpenAPI, AsyncAPI, and JSON Schema documents that drive design-first workflows, governance checks, and SDK generation. As I keep arguing, when the interface is captured as a clean, versioned specification it becomes the contract that both human developers and AI agents read to understand how to safely consume an API.