API Quick Reference

A condensed overview of all public types, traits, and functions across the a2a-rust crates.

Wire Types (`a2a-protocol-types`)

Core Types

Type	Description
`Task`	Unit of work with ID, status, history, artifacts
`TaskId`	Newtype wrapper for task identifiers
`TaskState`	Enum: Submitted, Working, InputRequired, AuthRequired, Completed, Failed, Canceled, Rejected
`TaskStatus`	State + optional message + timestamp
`TaskVersion`	Monotonically increasing version number
`ContextId`	Conversation context identifier

Messages

Type	Description
`Message`	Structured payload with ID, role, parts
`MessageId`	Newtype wrapper for message identifiers
`MessageRole`	Enum: User, Agent
`Part`	Content unit: text, file, or data
`PartContent`	Enum: Text, File, Data

Artifacts

Type	Description
`Artifact`	Result produced by an agent
`ArtifactId`	Newtype wrapper for artifact identifiers

Events

Type	Description
`StreamResponse`	Enum: Task, Message, StatusUpdate, ArtifactUpdate
`TaskStatusUpdateEvent`	Status change notification
`TaskArtifactUpdateEvent`	Artifact delivery notification

Agent Card

Type	Description
`AgentCard`	Root discovery document
`AgentInterface`	Transport endpoint descriptor
`AgentCapabilities`	Capability flags (streaming, push, extended card)
`AgentSkill`	Discrete agent capability
`AgentProvider`	Organization info

Parameters

Type	Description
`MessageSendParams`	SendMessage / SendStreamingMessage input
`SendMessageConfiguration`	Output modes, history, push config
`TaskQueryParams`	GetTask input
`ListTasksParams`	ListTasks input with filters and pagination
`CancelTaskParams`	CancelTask input
`TaskIdParams`	SubscribeToTask input

Push Notifications

Type	Description
`TaskPushNotificationConfig`	Webhook registration
`AuthenticationInfo`	Webhook auth credentials

Responses

Type	Description
`SendMessageResponse`	Enum: Task or Message
`TaskListResponse`	Paginated task list

Errors

Type	Description
`A2aError`	Protocol-level error
`ErrorCode`	Standard error codes
`A2aResult<T>`	Alias for `Result<T, A2aError>`

JSON-RPC

Type	Description
`JsonRpcRequest`	JSON-RPC 2.0 request envelope
`JsonRpcError`	JSON-RPC error object
`JsonRpcVersion`	Version marker (`"2.0"`)

Client (`a2a-protocol-client`)

Core Types

Type	Description
`A2aClient`	Main client for calling remote agents
`ClientBuilder`	Fluent builder for client configuration
`EventStream`	Async SSE event stream
`RetryPolicy`	Configurable retry with exponential backoff

Client Methods

Method	Returns	Description
`send_message(params)`	`SendMessageResponse`	Synchronous send
`stream_message(params)`	`EventStream`	Streaming send
`get_task(params)`	`Task`	Retrieve task by ID
`list_tasks(params)`	`TaskListResponse`	Query tasks
`cancel_task(id)`	`Task`	Cancel a running task
`subscribe_to_task(id)`	`EventStream`	Re-subscribe to task events
`set_push_config(config)`	`TaskPushNotificationConfig`	Create push config
`get_push_config(task_id, id)`	`TaskPushNotificationConfig`	Get push config
`list_push_configs(params)`	`ListPushConfigsResponse`	List push configs
`delete_push_config(task_id, id)`	`()`	Delete push config
`get_authenticated_extended_card(params)`	`AgentCard`	Get extended card

Interceptors

Type	Description
`CallInterceptor`	Request/response hook trait
`InterceptorChain`	Ordered interceptor sequence

Transport

Type	Description
`Transport`	Pluggable transport trait
`JsonRpcTransport`	JSON-RPC 2.0 transport
`RestTransport`	REST/HTTP transport

Server (`a2a-protocol-server`)

Core Types

Type	Description
`RequestHandler`	Central protocol orchestrator
`RequestHandlerBuilder`	Fluent builder for handler configuration
`RequestContext`	Information about the incoming request

Traits

Trait	Description
`AgentExecutor`	Agent logic entry point
`TaskStore`	Task persistence backend
`PushConfigStore`	Push config persistence
`PushSender`	Webhook delivery
`ServerInterceptor`	Server-side middleware
`AgentCardProducer`	Dynamic agent card generation
`Dispatcher`	HTTP dispatch trait (for `serve()`)

Dispatchers

Type	Description
`JsonRpcDispatcher`	JSON-RPC 2.0 HTTP dispatcher (implements `Dispatcher`)
`RestDispatcher`	RESTful HTTP dispatcher (implements `Dispatcher`)

Server Startup

Function	Description
`serve(addr, dispatcher)`	Bind + accept loop (blocking)
`serve_with_addr(addr, dispatcher)`	Bind + spawn, returns `SocketAddr`

Built-in Implementations

Type	Description
`InMemoryTaskStore`	In-memory task store with TTL
`InMemoryPushConfigStore`	In-memory push config store
`HttpPushSender`	HTTP webhook delivery with SSRF protection
`StaticAgentCardHandler`	Static agent card with HTTP caching
`DynamicAgentCardHandler`	Dynamic agent card with producer

Streaming

Type	Description
`EventEmitter`	Ergonomic event emission helper
`EventQueueWriter`	Write events to a stream
`EventQueueReader`	Read events from a stream
`EventQueueManager`	Manages stream lifecycle
`InMemoryQueueWriter`	Bounded channel writer
`InMemoryQueueReader`	Bounded channel reader

Configuration

Type	Description
`CorsConfig`	Cross-origin policy
`TaskStoreConfig`	TTL and capacity for in-memory store
`ServerError`	Server-level error type
`ServerResult<T>`	Alias for `Result<T, ServerError>`

SDK (`a2a-protocol-sdk`)

Modules

Module	Re-exports
`a2a_protocol_sdk::types`	All `a2a-protocol-types` exports
`a2a_protocol_sdk::client`	All `a2a-protocol-client` exports
`a2a_protocol_sdk::server`	All `a2a-protocol-server` exports
`a2a_protocol_sdk::prelude`	Most commonly used types

Prelude Contents

The prelude includes the most commonly used types from all three crates — see Project Structure for the full list.

Constructors Cheatsheet

#![allow(unused)]
fn main() {
// Task status
TaskStatus::new(TaskState::Working)
TaskStatus::with_timestamp(TaskState::Completed)

// Messages and parts
Part::text("hello")
Part::file_bytes(base64_string)
Part::file_uri("https://...")
Part::data(json_value)

// Artifacts
Artifact::new("artifact-id", vec![Part::text("content")])

// IDs
TaskId::new("task-123")
ContextId::new("ctx-456")
MessageId::new("msg-789")

// Capabilities (non_exhaustive — use builder)
AgentCapabilities::none()
    .with_streaming(true)
    .with_push_notifications(false)

// Push configs
TaskPushNotificationConfig::new("task-id", "https://webhook.url")
}

Next Steps

Changelog — Version history
Configuration Reference — All tunable parameters