docs: Document supported GRPC transport (#306)

# Description

Integration of gRpc spec in the documentation

Author: guglielmo-san

README.md

@@ -29,6 +29,14 @@ If you plan to use the Express integration (imports from `@a2a-js/sdk/server/exp
 npm install express
 ```
 
+### For gRPC Usage
+
+If you plan to use the GRPC transport (imports from `@a2a-js/sdk/server/grpc` or `@a2a-js/sdk/client/grpc`), you must install the required peer dependencies:
+
+```bash
+npm install @grpc/grpc-js @bufbuild/protobuf
+```
+
 You can also find some samples [here](https://github.com/a2aproject/a2a-js/tree/main/src/samples).
 
 ---
@@ -41,7 +49,7 @@ This SDK implements the A2A Protocol Specification [`v0.3.0`](https://a2a-protoc
 | :--- | :---: | :---: |
 | **JSON-RPC** | ✅ | ✅ |
 | **HTTP+JSON/REST** | ✅ | ✅ |
-| **gRPC** | ❌ | ❌ |
+| **GRPC** (Node.js only) | ✅ | ✅ |
 
 ## Quickstart
 
@@ -54,6 +62,7 @@ The core of an A2A server is the `AgentExecutor`, which contains your agent's lo
 ```typescript
 // server.ts
 import express from 'express';
+import { Server, ServerCredentials } from '@grpc/grpc-js';
 import { v4 as uuidv4 } from 'uuid';
 import { AgentCard, Message, AGENT_CARD_PATH } from '@a2a-js/sdk';
 import {
@@ -64,6 +73,7 @@ import {
   InMemoryTaskStore,
 } from '@a2a-js/sdk/server';
 import { agentCardHandler, jsonRpcHandler, restHandler, UserBuilder } from '@a2a-js/sdk/server/express';
+import { grpcService, A2AService } from '@a2a-js/sdk/server/grpc';
 
 // 1. Define your agent's identity card.
 const helloAgentCard: AgentCard = {
@@ -81,6 +91,7 @@ const helloAgentCard: AgentCard = {
   additionalInterfaces: [
     { url: 'http://localhost:4000/a2a/jsonrpc', transport: 'JSONRPC' }, // Default JSON-RPC transport
     { url: 'http://localhost:4000/a2a/rest', transport: 'HTTP+JSON' }, // HTTP+JSON/REST transport
+    { url: 'localhost:4001', transport: 'GRPC' }, // GRPC transport
   ],
 };
 
@@ -123,6 +134,15 @@ app.use('/a2a/rest', restHandler({ requestHandler, userBuilder: UserBuilder.noAu
 app.listen(4000, () => {
   console.log(`🚀 Server started on http://localhost:4000`);
 });
+
+const server = new Server();
+server.addService(A2AService, grpcService({
+  requestHandler,
+  userBuilder: UserBuilder.noAuthentication,
+}));
+server.bindAsync(`localhost:4001`, ServerCredentials.createInsecure(), () => {
+  console.log(`🚀 Server started on localhost:4001`);
+});
 ```
 
 ### Client: Sending a Message
@@ -163,6 +183,46 @@ async function run() {
 await run();
 ```
 
+### gRPC Client: Sending a Message
+
+The [`ClientFactory`](src/client/factory.ts) has to be created explicitly passing the [`GrpcTransportFactory`](src/client/transports/grpc/grpc_transport.ts).
+
+```typescript
+// client.ts
+import { ClientFactory, ClientFactoryOptions } from '@a2a-js/sdk/client';
+import { GrpcTransportFactory } from '@a2a-js/sdk/client/grpc';
+import { Message, MessageSendParams, SendMessageSuccessResponse } from '@a2a-js/sdk';
+import { v4 as uuidv4 } from 'uuid';
+
+async function run() {
+  const factory = new ClientFactory({
+    transports: [new GrpcTransportFactory()]
+  });
+
+  // createFromUrl accepts baseUrl and optional path,
+  // (the default path is /.well-known/agent-card.json)
+  const client = await factory.createFromUrl('http://localhost:4000');
+
+  const sendParams: MessageSendParams = {
+    message: {
+      messageId: uuidv4(),
+      role: 'user',
+      parts: [{ kind: 'text', text: 'Hi there!' }],
+      kind: 'message',
+    },
+  };
+
+  try {
+    const response = await client.sendMessage(sendParams);
+    const result = response as Message;
+    console.log('Agent response:', result.parts[0].text); // "Hello, world!"
+  } catch(e) {
+    console.error('Error:', e);
+  }
+}
+
+await run();
+```
 ---
 
 ## A2A `Task` Support

tck/agent/index.ts

@@ -240,7 +240,7 @@ async function main() {
   const server = new Server();
   server.addService(A2AService, grpcHandlerInstance);
   server.bindAsync(`localhost:${GRPC_PORT}`, ServerCredentials.createInsecure(), () => {
-    console.log(`[SUTAgent] gRPC server running at http://localhost:${GRPC_PORT}`);
+    console.log(`[SUTAgent] gRPC server running at localhost:${GRPC_PORT}`);
   });
 }