a2a-protocol-server 0.4.0

A2A protocol v1.0 — server framework (hyper-backed)
Documentation 
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// SPDX-License-Identifier: Apache-2.0
// Copyright 2026 Tom F.
//
// A2A protocol v1.0 — gRPC service definition.
//
// This binding uses JSON-encoded payloads over gRPC framing, providing
// HTTP/2 multiplexing and native server-streaming while reusing the
// canonical JSON wire format from the A2A specification.
//
// Each RPC method corresponds to an A2A JSON-RPC method. Request and
// response payloads are the same JSON structures used by the JSON-RPC
// and REST bindings, wrapped in a `bytes` field for transport.

syntax = "proto3";

package a2a.v1;

// JSON payload wrapper.
//
// The `data` field contains a UTF-8 JSON document. For requests this is
// the method-specific params object; for responses it is the result
// object (or a serialized A2aError on failure).
message JsonPayload {
  bytes data = 1;
}

// Metadata key for passing the A2A protocol version.
// Clients SHOULD set `a2a-version: 1.0.0` in gRPC metadata.

// Metadata key for tenant identification in multi-tenant deployments.
// Clients MAY set `a2a-tenant` in gRPC metadata.

// A2A gRPC service.
//
// All methods use JSON-encoded payloads so that the same serde types
// work across JSON-RPC, REST, and gRPC bindings without duplication.
service A2aService {
  // ── Messaging ──────────────────────────────────────────────────

  // Sends a message to the agent and waits for a response.
  rpc SendMessage(JsonPayload) returns (JsonPayload);

  // Sends a message and streams back status/artifact updates.
  rpc SendStreamingMessage(JsonPayload) returns (stream JsonPayload);

  // ── Task lifecycle ─────────────────────────────────────────────

  // Retrieves a task by ID.
  rpc GetTask(JsonPayload) returns (JsonPayload);

  // Lists tasks with optional filters.
  rpc ListTasks(JsonPayload) returns (JsonPayload);

  // Cancels a running task.
  rpc CancelTask(JsonPayload) returns (JsonPayload);

  // Subscribes to updates for an existing task.
  rpc SubscribeToTask(JsonPayload) returns (stream JsonPayload);

  // ── Push notification config ───────────────────────────────────

  // Creates or updates a push notification configuration.
  rpc CreateTaskPushNotificationConfig(JsonPayload) returns (JsonPayload);

  // Retrieves a push notification configuration.
  rpc GetTaskPushNotificationConfig(JsonPayload) returns (JsonPayload);

  // Lists push notification configurations for a task.
  rpc ListTaskPushNotificationConfigs(JsonPayload) returns (JsonPayload);

  // Deletes a push notification configuration.
  rpc DeleteTaskPushNotificationConfig(JsonPayload) returns (JsonPayload);

  // ── Agent card ─────────────────────────────────────────────────

  // Returns the extended agent card (requires authentication).
  rpc GetExtendedAgentCard(JsonPayload) returns (JsonPayload);
}