Decorators

Every AsyncAPI-specific decorator is declared in lib/main.tsp and accepts both {} (model expression) and #{} (value literal) syntax. Decorators that misconfigure emit compile-time diagnostics — see Diagnostics.

Core messaging

Decorator	Target	Purpose
`@channel(address, description?)`	Operation	Defines a channel address
`@publish` / `@subscribe`	Operation	Marks operation as send / receive
`@reply(replyModel, address?)`	Operation	Operation reply with message reference

Servers

Decorator	Target	Purpose
`@server(name, config)`	Namespace	Defines server (url, protocol, description, variables)
`@useChannelServer(name)`	Operation	Binds a channel to a specific server

Messages

Decorator	Target	Purpose
`@message(config)`	Model	Message metadata (title, contentType, description, examples)
`@messageId(id)`	Model	Overrides auto-generated message key
`@header(name, value?)`	Model / ModelProperty	Defines message headers
`@correlationId(location)`	Model	Correlation ID runtime expression for message tracing

Protocols and bindings

Decorator	Target	Purpose
`@protocol(config)`	Operation / Model	Protocol-specific config at spec-correct placements
`@bindings(config)`	Operation / Model / Namespace	Generic protocol bindings (auto-versioned, placement-checked)
`@reusableBinding(name, config)`	Namespace	Declares a reusable binding
`@useBinding(name)`	Operation / Model / Namespace	References a reusable binding
`@useChannelBinding(name)`	Operation	References a reusable channel binding

See Protocol Bindings for per-protocol placement rules.

Security

Decorator	Target	Purpose
`@security(config)`	Operation / Namespace	Declares security schemes (oauth2, httpApiKey, scramSha512, …)
`@operationSecurity(config)`	Operation	Attaches security requirements to one operation

See Security for scheme details.

Document metadata

Decorator	Target	Purpose
`@apiVersion(version)`	Namespace	Sets `info.version`
`@defaultContentType(type)`	Namespace	Sets `defaultContentType` on document root
`@operationId(id)`	Operation	Overrides auto-generated operation key
`@jsonSchemaExtension(key, value)`	Model / ModelProperty / Union / Enum / Scalar	Arbitrary JSON Schema keywords, repeatable
`@extension(key, value)`	Namespace / Operation / Model	AsyncAPI `x-` spec extensions (root / operation / message objects)
`@tags(value)`	Model / Operation / Namespace	Tags (strings or rich objects)

Reusable components

Decorator	Target	Purpose
`@operationTrait(name, config)`	Namespace	Declares `components.operationTraits` entry
`@useOperationTrait(name)`	Operation	References an operation trait
`@messageTrait(name, config)`	Namespace	Declares `components.messageTraits` entry
`@useMessageTrait(name)`	Model	References a message trait
`@parameter(name, config)`	Namespace	Declares `components.parameters` for channel address templating
`@reusableCorrelationId(name, location)`	Namespace	Declares `components.correlationIds` entry
`@useCorrelationId(name)`	Model	References a reusable correlation ID

See Reusable Components for worked examples.

Standard TypeSpec decorators

These come from @typespec/compiler and are fully supported: @pattern, @minValue, @maxValue, @minLength, @maxLength, @format, @minItems, @maxItems, @doc, @summary (maps to title), @example (maps to examples), @visibility (maps to readOnly/writeOnly), @encodedName, @encode, #deprecated, and default values via prop: Type = value.

Where to go next

Schema Generation — how models and constraints become JSON Schema
Security — the 13 valid scheme types
Emitter Options — output format and file layout