Decorators

The package mirrors @nestjs/swagger naming. Five decorators describe the AsyncAPI 3.0 model, and three optional decorators attach protocol bindings (see Bindings).

@AsyncApiChannel(id, options?)

Class-level. Declares the AsyncAPI 3.0 channel a handler class operates on, mirroring how @Controller('path') declares an HTTP base route. The channel id is explicit by design — the generator never derives it from the class name.

@AsyncApiChannel('orders', {
  address: 'orders.v1',
  title: 'Orders',
  description: 'Lifecycle events for customer orders.',
})
export class OrdersHandler {}

Option	Purpose
address	Channel address (topic, queue, routing key). Defaults to the id; pass null to mark an address unknown at design time
title	Human-friendly channel title
summary	Short channel summary
description	Verbose channel description

@AsyncApiPub(options?) / @AsyncApiSub(options?)

Method-level. Declare an AsyncAPI 3.0 operation on a channel handler method. @AsyncApiPub produces a send operation; @AsyncApiSub produces a receive operation. The action is fixed by the decorator and is not configurable.

@AsyncApiPub({ operationId: 'orderPlaced', summary: 'A customer placed an order.' })
publishOrderPlaced(): void {}

@AsyncApiSub({ operationId: 'onOrderPlaced' })
handleOrderPlaced(): void {}

Option	Purpose
operationId	Key in the generated operations map. Defaults to the method name
title	Human-friendly operation title
summary	Short operation summary
description	Verbose operation description

The 3.0 naming flips relative to 2.x: a send operation is @AsyncApiPub, and a receive operation is @AsyncApiSub. See Migration.

@AsyncApiMessage(payload, options?)

Method-level. Declares the payload of the message an operation sends or receives. The payload is either a DTO class — turned into JSON Schema through the same @nestjs/swagger chain that documents HTTP bodies — or a pre-computed { name, schema } source (for example a Zod schema converted with z.toJSONSchema()). The message is registered once in components.messages and referenced from the channel and operation.

@AsyncApiMessage(OrderPlacedDto, {
  name: 'OrderPlaced',
  summary: 'A customer placed an order.',
})
publishOrderPlaced(): void {}

Option	Purpose
name	components.messages key and message name. Defaults to the DTO class name or the schema source name
title	Human-friendly message title
summary	Short message summary
description	Verbose message description
contentType	Payload content type. Defaults to application/json

@AsyncApiHeaders(headers)

Method-level. Declares the headers of the message an operation sends or receives, resolved exactly as the payload is — a DTO class through the @nestjs/swagger chain, or a pre-computed { name, schema }.

@AsyncApiMessage(OrderPlacedDto)
@AsyncApiHeaders(OrderHeadersDto)
publishOrderPlaced(): void {}

@AsyncApiServer(name, host, protocol, options?)

Class-level and repeatable. Declares a broker the application connects to. Stacking it declares several brokers, and every declaration across the application is merged into the document's servers map. The protocol and the optional protocol bindings carry the transport identity and connection metadata.

@AsyncApiServer('kafka', 'kafka.example.com:9092', 'kafka', {
  title: 'Kafka cluster',
  bindings: { kafka: { bindingVersion: '0.5.0' } },
})
@AsyncApiServer('nats', 'nats.example.com:4222', 'nats')
export class OrdersHandler {}

Argument / option	Purpose
name	Key in the generated servers map
host	Server host (may include the port)
protocol	Connection protocol (kafka, nats, mqtt, amqp, …)
protocolVersion	Protocol version used for connection
pathname	Path to a resource in the host
title / summary / description	Server metadata
bindings	Protocol-specific connection bindings, keyed by protocol

Binding Decorators

Three optional decorators attach protocol-specific bindings:

• @AsyncApiChannelBindings(bindings) — class-level, alongside @AsyncApiChannel.
• @AsyncApiOperationBindings(bindings) — method-level, alongside the operation.
• @AsyncApiMessageBindings(bindings) — method-level, alongside the message.

See Bindings for the full Kafka, NATS, MQTT, and AMQP binding shapes.