API Specifications

Resources

• OpenAPI Specification (OAS)
  The OpenAPI Specification (formerly Swagger) is the dominant industry standard for describing HTTP-based RESTful APIs. OAS describes endpoints, operations, parameters, request/response schemas, authentication, and examples in a machine- an…
• AsyncAPI Specification
  AsyncAPI is the open standard for describing event-driven and message-driven APIs across protocols such as Kafka, AMQP, MQTT, WebSocket, NATS, and SNS/SQS. AsyncAPI 3.0 (December 2023) decoupled operations from channels, enabling clearer m…
• JSON Schema
  JSON Schema is a declarative language for annotating and validating JSON documents. It is the foundational schema language for most modern API specifications (OpenAPI 3.1, AsyncAPI 3, and others embed it directly). The current stable diale…
• JSON Structure
  JSON Structure is an emerging open specification that extends and complements JSON Schema with a clearer, more code-generation-friendly type system designed for data contracts and modeling. It introduces structural primitives intended for…
• GraphQL SDL
  GraphQL is a query language and runtime for APIs, defined by the GraphQL Specification. The GraphQL Schema Definition Language (SDL) is the declarative format used to define types, queries, mutations, and subscriptions on a GraphQL server.…
• gRPC and Protocol Buffers
  gRPC is a high-performance RPC framework using HTTP/2 and Protocol Buffers (Protobuf) as its IDL and wire format. Service definitions are written in .proto files. gRPC is a CNCF graduated project; Protocol Buffers (proto2/proto3, with prot…
• Smithy
  Smithy is an open-source IDL and code-generation framework for defining services and SDKs, created and maintained by AWS. It is protocol-agnostic (HTTP REST, AWS JSON, MQTT, RPC), supports traits-based modeling, and is used to generate AWS…
• TypeSpec
  TypeSpec (formerly Cadl) is a language for describing API shapes developed by Microsoft. TypeSpec definitions emit OpenAPI 3.x, JSON Schema, Protobuf, and other artifacts, and serve as the upstream source for Azure SDK generation. TypeSpec…
• RAML (RESTful API Modeling Language)
  RAML is a YAML-based modelling language for RESTful APIs, originally created by Mulesoft. RAML 1.0 (2016) is the current stable specification. RAML governance has effectively converged with Mulesoft / Salesforce, and the broader industry h…
• API Blueprint
  API Blueprint is a Markdown-based specification language for describing web APIs, originally created by Apiary (acquired by Oracle). The spec is MIT licensed but development effectively stalled after Oracle's acquisition of Apiary; it is d…
• WSDL / SOAP
  The Web Services Description Language (WSDL) is the historical XML-based interface definition language for SOAP web services. WSDL 1.1 (2001) is the most widely deployed version; WSDL 2.0 is a W3C Recommendation (2007). SOAP and WSDL are g…
• JSON-RPC 2.0
  JSON-RPC 2.0 is a stateless, light-weight remote procedure call (RPC) protocol encoded in JSON. It is widely used in blockchain/Web3 APIs (Ethereum, Bitcoin), IDE language servers (LSP), and developer tooling. The 2.0 specification (2010)…
• Tinybird API Spec
  The Tinybird API specification is a vendor-defined, declarative format for describing analytics endpoints (pipes), data sources, and parameters backed by ClickHouse. It is documented here as a representative example of vendor-specific spec…

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