a2a_protocol_core

Crate: a2a_protocol_core · Path: crates/a2a_protocol_core
Description (Cargo.toml): Pure A2A (Agent-to-Agent) protocol domain logic - WASM optimized

Role

Pure A2A v1.0.0 domain layer, completely transport-agnostic. Defines all protocol types (AgentCard, Task, Message, Artifact), JSON-RPC method params, security schemes, agent discovery, the method registry, and in-memory task storage. No HTTP, no Spin SDK — just domain logic that compiles everywhere.

Feature flags

From crates/a2a_protocol_core/Cargo.toml:

Feature	Purpose
`default`	Enables `protocol-core`
`protocol-core`	Base Task + Message + AgentCard types (`data`, `methods`, `services` modules)
`event-stream`	SSE streaming support (`streaming` module); requires `protocol-core`
`file-handling`	File upload/download support; requires `protocol-core`
`time-stamps`	Timestamp support for Task/Message via `chrono`
`all-features`	Enables `event-stream`, `file-handling`, `time-stamps`
`spec-compliant`	Core A2A spec features (`protocol-core` + `event-stream`)
`wasm-optimized`	Minimal features for WASM targets (`protocol-core` only)
`core`	Backward-compat alias for `protocol-core`
`streaming`	Backward-compat alias for `event-stream`
`timestamps`	Backward-compat alias for `time-stamps`
`push-notifications`	Push notification support; requires `protocol-core`
`extended-discovery`	Extended agent discovery; requires `protocol-core`

Public API (from `src/lib.rs`)

Modules: agent, error, protocol, registry, security, transport, data (feature protocol-core), methods (feature protocol-core), streaming (feature event-stream), services (feature protocol-core)

Always-available types:

AgentCard, AgentCapabilities, AgentCardSignature, AgentExtension, AgentInterface, AgentProvider, AgentSkill
A2AError, A2AResult, a2a_error_codes
A2AProtocol
A2AMethodRegistry, A2AMethodHandler, A2ANotificationHandler, MethodMetadata, RegistryStats
Security: SecurityScheme, SecurityRequirement, ApiKeySecurityScheme, HttpAuthSecurityScheme, OAuth2SecurityScheme, OAuthFlows, OpenIdConnectSecurityScheme, MutualTlsSecurityScheme, and OAuth flow types
A2ATransport, A2ATransportFactory traits

Feature-gated types (protocol-core):

Task, TaskState, TaskStatus, TaskPushNotificationConfig
Message, MessageRole, Part, Artifact, AuthenticationInfo
SendMessageRequest, SendMessageResponse, MessageSendParams, TaskGetParams, TaskListParams, TaskCancelParams, and related param/response types
AgentDiscovery, DefaultAgentDiscovery
TaskStorage, InMemoryTaskStorage, ConversationContext

Re-exports from protocol_transport_core: JsonRpcError, JsonRpcId, JsonRpcIncoming, JsonRpcRequest, JsonRpcResponse, JSONRPC_VERSION, jsonrpc_error_codes

Constant: A2A_PROTOCOL_VERSION ("1.0")

Example sketch

use a2a_protocol_core::{AgentCard, AgentSkill, Task, TaskState, Message, MessageRole, Part};

let card = AgentCard::new("my-agent".to_string());

let message = Message {
    role: MessageRole::User,
    parts: vec![Part::text("Hello, agent!")],
    ..Default::default()
};

Full API reference: cargo doc -p a2a_protocol_core --no-deps --all-features