Problem Details (RFC 9457)

A URI reference that identifies the problem type. It is the primary identifier for the error category and should be dereferenceable to human-readable documentation.

• Absolute URI: Recommended for global types (e.g., https://api.example.com/errors/out-of-stock).
• Relative URI: Can be used for types specific to the local API context.
• This member is optional, but its use is strongly encouraged to allow clients to programmatically identify the error.

A short, human-readable summary of the problem type. It should be consistent for the same type and should not change from occurrence to occurrence.

• Example: "Out of Stock", "Validation Failed", "Access Denied".
• This is a recommended member. It provides a concise, static title for the error category, distinct from the instance-specific detail.

The HTTP status code generated by the origin server for this occurrence of the problem. It mirrors the status code in the HTTP response header.

• Example: 404, 422, 500.
• This member is optional but highly useful, as it allows the problem detail to be processed independently of the HTTP headers.

A human-readable explanation specific to this occurrence of the problem. It provides instance-specific details that the title does not.

• Example: "The product with SKU 'ABC-123' is no longer available in the requested size 'Large'."
• This is an optional member. It is the primary place for actionable, contextual error information for end-users or developers.

A URI reference that identifies the specific occurrence of the problem. It may point to a log entry, a specific resource, or a unique error ID.

• Example: "/log/errors/550e8400-e29b-41d4-a716-446655440000"
• This is an optional member. It is extremely valuable for debugging, allowing support teams to locate the exact error event in backend systems.

Problem Details objects may include additional members beyond the core five to provide further machine-readable context.

• Namespace: Extension members should avoid conflict with core members and other extensions. Using a vendor-specific prefix (e.g., accountId, invalidParams) is a common practice.
• Use Case: Common extensions include invalidParams for validation error details or balance for a financial API error.
• The standard explicitly allows for this extensibility to support domain-specific error information.

The OpenAPI Specification (OAS) is the industry-standard, machine-readable format for describing RESTful APIs. It defines endpoints, operations, parameters, authentication methods, and data models.

• Serves as the foundational API contract between providers and consumers.
• Enables automated code generation for client SDKs and server stubs.
• Provides the structural blueprint that AI agents parse during schema ingestion to understand available tools.

JSON Schema is a declarative language for annotating, validating, and documenting the structure of JSON data. It defines allowed data types, formats, constraints, and relationships.

• Used within OpenAPI to define the precise shape of request and response payloads.
• Enforces schema validation to ensure data correctness before and after API calls.
• Critical for providing structured output guarantees from AI models, ensuring generated parameters are type-safe.

Contract testing is a methodology for verifying that two services (e.g., an AI agent and a backend API) adhere to a shared interface definition. It tests the contract, not the implementation.

• Ensures that the consumer's expectations, derived from the API schema, match the provider's actual responses.
• Catches breaking changes before deployment, supporting safe schema evolution.
• A key practice for maintaining integration reliability in API First Design.

Dynamic invocation is the runtime construction and execution of API calls based on a machine-readable schema, rather than using hardcoded client libraries.

• The core mechanism enabling AI agents to call arbitrary external tools described by an OpenAPI spec.
• Involves programmatically resolving endpoints, serializing parameters per JSON Schema, and handling the response.
• Requires robust error handling and retry logic to manage API failures gracefully.

API gateway integration involves configuring an API gateway to use an OpenAPI schema as its source of truth for routing, security, and validation.

• The gateway can perform automatic request/response validation against the schema, rejecting malformed calls.
• Enforces authentication, rate limiting, and transforms requests, acting as a zero-trust API gateway for agent traffic.
• Often the point where Problem Details error responses are standardized and returned to the client.

AsyncAPI is an open-source specification, modeled on OpenAPI, for describing asynchronous, event-driven APIs that use protocols like Kafka, MQTT, or WebSockets.

• Defines message formats, channels, and operations for event producers and consumers.
• Enables the same machine-readable tooling and code generation for event-based architectures.
• Extends the concept of a machine-readable contract beyond request/response to pub/sub and streaming integrations.