a2a_protocol_core 0.1.1

Pure A2A (Agent-to-Agent) protocol domain logic - WASM optimized
Documentation

a2a_protocol_core

Pure A2A (Agent-to-Agent) Protocol v1.0 domain logic. Transport-agnostic, WASM-first, no HTTP dependencies.

Role in the stack

a2a_http_server  ──► a2a_protocol_core  ──► protocol_transport_core (JSON-RPC 2.0)
a2a_http_client  ──► a2a_protocol_core
agent_sdk        ──► a2a_protocol_core

This crate owns the protocol state machine, method registry, data types, and task storage. It never touches sockets or HTTP.

Quick start

use a2a_protocol_core::{A2AProtocol, AgentCard, methods::messaging::handle_message_send};
use a2a_protocol_core::services::InMemoryTaskStorage;
use std::sync::Arc;

let card = AgentCard::new("my-agent")
    .with_capability("SendMessage", "Process user messages");

let storage = Arc::new(InMemoryTaskStorage::new());
let mut protocol = A2AProtocol::new(card, storage);

// Register method handlers
protocol.register_method("SendMessage", Arc::new(|req, storage| {
    handle_message_send(req, storage).map_err(Into::into)
}));

// Dispatch a JSON-RPC request
let request = serde_json::from_str(raw_bytes)?;
let response = protocol.handle_request(request)?;

Feature flags

Flag Enables Default
protocol-core Task, Message, Artifact, AgentCard, TaskStorage yes
event-stream StreamResponse, SendStreamingMessage handler no
file-handling URL and raw-bytes Part variants in should_create_task no
time-stamps chrono-based timestamps on discovery responses no
all-features All of the above no
spec-compliant protocol-core + event-stream (A2A spec minimum) no
wasm-optimized protocol-core only (smallest WASM footprint) no

Module overview

Module Contents
agent AgentCard, AgentCapabilities, AgentSkill, builder methods
protocol A2AProtocol — method registry + request dispatcher
registry A2AMethodRegistry, A2AMethodHandler, MethodMetadata
error A2AError, A2AResult, a2a_error_codes constants
transport A2ATransport trait, A2ATransportFactory
security SecurityScheme union (ApiKey, HTTP, OAuth2, OIDC, mTLS)
data::task Task, TaskStatus, TaskState
data::message Message, MessageRole, Part
data::artifact Artifact
data::notification TaskPushNotificationConfig, AuthenticationInfo
methods::messaging handle_message_send, handle_tasks_send_subscribe
methods::tasks handle_tasks_get, handle_tasks_cancel, handle_tasks_list
methods::params All request/response param types
methods::discovery DefaultAgentDiscovery, AgentDiscovery trait
services::task_storage TaskStorage trait, InMemoryTaskStorage
streaming StreamResponse, TaskStatusUpdateEvent, TaskArtifactUpdateEvent

A2A error codes

use a2a_protocol_core::a2a_error_codes;

a2a_error_codes::TASK_NOT_FOUND           // -32001
a2a_error_codes::TASK_NOT_CANCELABLE      // -32002
a2a_error_codes::PUSH_NOTIFICATION_NOT_SUPPORTED // -32003
a2a_error_codes::UNSUPPORTED_OPERATION    // -32004
a2a_error_codes::CONTENT_TYPE_NOT_SUPPORTED // -32005
a2a_error_codes::INVALID_AGENT_RESPONSE   // -32006
a2a_error_codes::EXTENDED_AGENT_CARD_NOT_CONFIGURED // -32007
// Platform extensions (-32050 range):
a2a_error_codes::AUTHENTICATION_FAILED   // -32050
a2a_error_codes::AUTHORIZATION_FAILED    // -32051
a2a_error_codes::RATE_LIMIT_EXCEEDED     // -32052
a2a_error_codes::CAPACITY_EXCEEDED       // -32053

Design constraints

  • No HTTP, no sockets. This crate compiles to pure WASM (wasm32-unknown-unknown) with zero platform deps.
  • Sync-only public API. Async is handled by the server/client adapters above this layer.
  • Handler functions are not re-exported at the crate root. Access them via methods::messaging::handle_* and methods::tasks::handle_*.