AsyncAPI is an open specification for defining and documenting event-driven and asynchronous APIs in a machine-readable format. It describes message channels, payloads, bindings, and operations across protocols such as Kafka, MQTT, AMQP, and WebSockets, enabling tooling, code generation, and documentation.
AsyncAPI
AsyncAPI is the open specification for describing event-driven and asynchronous APIs in a machine-readable way — the counterpart to OpenAPI for the world of messages, streams, and events rather than request-response. It documents the channels a system publishes and subscribes to, the shape of the messages that flow through them, and the protocol bindings that carry them, so that the same document can drive documentation, code generation, and validation. It was created in 2017 and now lives under the Linux Foundation alongside the other core API specifications.
- Channels, messages, and operations - The spec describes what a service publishes and consumes, not just endpoints you call.
- Protocol-agnostic bindings - One document can cover Kafka, MQTT, AMQP, WebSockets, and more through protocol-specific bindings.
- Shared schema tooling - Payloads are defined with JSON Schema, so message contracts reuse the same modeling as the rest of the API stack.
- Full tooling ecosystem - Generators, validators, and documentation renderers turn the contract into working artifacts.
In real API operations, AsyncAPI is how a provider makes its streaming and event surface as governable as its REST surface — and in the sectors I score, its absence is conspicuous. Across banking and market data, the mandated or documented request-response pipes are covered while the event side goes undescribed, leaving roughly half the artifact family unbuilt. As agents begin to consume real-time and event-driven APIs, an AsyncAPI document is what makes that surface discoverable and safe to automate against rather than a black box.
Referenced in API Evangelist papers
This standard shows up in my published research. These reports read the machine-readable evidence provider by provider — and put this standard in the context of a real sector.
The State of Telecom APIs
Zero of twenty-eight aggregators publish an AsyncAPI, in a layer whose webhooks are universal.
The State of US Insurance APIs
No first-party AsyncAPI anywhere in US insurance, in a sector whose real integration idiom is asynchronous.
The State of Australian Banking APIs
The event surface missing above the mandated GET-only CDR pipes.
The State of Market Data APIs
The streaming surface is missing on 39% of market data providers — half the artifact family is unbuilt.
Referenced on the API Evangelist blog
Where this standard shows up across sixteen years of my writing at apievangelist.com — how it fits into API design, governance, and the agentic turn.
AsyncAPI Version 2.0 Is Ready For Use
2019-09-11
OpenAPI is the HTTP Binding in AsyncAPI
2020-07-20
