# AsyncAPI — Open Standard for Event-Driven API Documentation

> AsyncAPI is an open specification for defining asynchronous APIs. It provides a machine-readable format for documenting message-driven architectures using protocols like Kafka, MQTT, WebSocket, and AMQP, with tooling for code generation and validation.

## Install

Save as a script file and run:

# AsyncAPI — Open Standard for Event-Driven API Documentation

## Quick Use
```bash
# Install the AsyncAPI CLI
npm install -g @asyncapi/cli
# Create a new AsyncAPI document from a template
asyncapi new
# Validate an existing spec file
asyncapi validate asyncapi.yaml
# Generate documentation
asyncapi generate fromTemplate asyncapi.yaml @asyncapi/html-template -o docs/
```

## Introduction
AsyncAPI is an open specification, similar to OpenAPI but designed for event-driven and message-based APIs. It lets teams describe the channels, messages, and schemas their services produce and consume, enabling automated documentation, code generation, and contract testing for asynchronous architectures.

## What AsyncAPI Does
- Defines a YAML/JSON schema for describing message brokers, channels, and message payloads
- Generates human-readable documentation from specification files
- Produces server and client code stubs in multiple languages
- Validates messages against defined schemas for contract testing
- Supports protocol bindings for Kafka, MQTT, AMQP, WebSocket, NATS, and more

## Architecture Overview
The AsyncAPI ecosystem has three layers: the specification itself (a JSON Schema-based format), a set of parsers that read and validate spec documents, and a toolchain of generators and UIs. The CLI orchestrates these components. The spec parser resolves references and produces an in-memory document model. Generators consume this model through Nunjucks or React-based templates to produce output (docs, code, diagrams).

## Self-Hosting & Configuration
- Install the CLI via npm, Homebrew, or Docker
- Spec files are plain YAML or JSON; no server infrastructure required
- AsyncAPI Studio (web IDE) can be self-hosted as a static site
- Generator templates are published as npm packages and can be customized
- CI integration via the CLI for spec validation in pull request checks

## Key Features
- Protocol-agnostic: supports Kafka, MQTT, AMQP, WebSocket, Solace, NATS, and more
- Code generation for TypeScript, Java, Python, Go, and other languages
- AsyncAPI Studio provides a visual editor with live preview
- Schema reuse via JSON Schema references and traits
- Community-maintained generator templates for common frameworks

## Comparison with Similar Tools
- **OpenAPI (Swagger)** — designed for REST/HTTP APIs; AsyncAPI covers event-driven protocols
- **CloudEvents** — defines a common event envelope format; AsyncAPI documents the full API contract including channels and bindings
- **Avro/Protobuf** — schema formats for serialization; AsyncAPI wraps around these to describe the broader messaging architecture
- **Smithy (AWS)** — API modeling language; AsyncAPI is more community-driven and protocol-neutral
- **RAML** — API description language; AsyncAPI specifically targets asynchronous patterns

## FAQ
**Q: How does AsyncAPI relate to OpenAPI?**
A: AsyncAPI was inspired by OpenAPI and shares similar structure. OpenAPI describes synchronous HTTP APIs; AsyncAPI describes asynchronous message-based APIs. They can be used together in a system with both REST and event-driven components.

**Q: What protocols does AsyncAPI support?**
A: Kafka, MQTT, AMQP 0-9-1, AMQP 1.0, WebSocket, NATS, JMS, Solace, Google Pub/Sub, Amazon SNS/SQS, and others via protocol bindings.

**Q: Can I generate server code from an AsyncAPI document?**
A: Yes. The generator tool produces code stubs in multiple languages. Templates exist for Node.js, Java Spring, and Python, among others.

**Q: Is AsyncAPI a CNCF or Linux Foundation project?**
A: AsyncAPI is part of the Linux Foundation, giving it vendor-neutral governance and long-term sustainability.

## Sources
- https://github.com/asyncapi/spec
- https://www.asyncapi.com

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Source: https://tokrepo.com/en/workflows/asset-ea7c8b80
Author: Script Depot