docs: comprehensive feature documentation for SEP-1730 Tier 1 (#1548)

docs/client.md

@@ -58,3 +58,53 @@ These examples show how to:
 - Perform dynamic client registration if needed.
 - Acquire access tokens.
 - Attach OAuth credentials to Streamable HTTP requests.
+
+## stdio transport
+
+Use `StdioClientTransport` to connect to a server that runs as a local child process:
+
+```typescript
+import { Client } from '@modelcontextprotocol/sdk/client/index.js';
+import { StdioClientTransport } from '@modelcontextprotocol/sdk/client/stdio.js';
+
+const transport = new StdioClientTransport({
+    command: 'node',
+    args: ['server.js'],
+    env: { NODE_ENV: 'production' },
+    cwd: '/path/to/server'
+});
+
+const client = new Client({ name: 'my-client', version: '1.0.0' });
+await client.connect(transport);
+// connect() calls transport.start() automatically, spawning the child process
+```
+
+The transport communicates over the child process's stdin/stdout using JSON-RPC. The `stderr` option controls where the child's stderr goes (defaults to `'inherit'`).
+
+## Roots
+
+Roots let a client expose filesystem locations to the server, so the server knows which directories or files are relevant. Declare the `roots` capability and register a handler:
+
+```typescript
+import { Client } from '@modelcontextprotocol/sdk/client/index.js';
+import { ListRootsRequestSchema } from '@modelcontextprotocol/sdk/types.js';
+
+const client = new Client({ name: 'my-client', version: '1.0.0' }, { capabilities: { roots: { listChanged: true } } });
+
+client.setRequestHandler(ListRootsRequestSchema, async () => {
+    return {
+        roots: [
+            { uri: 'file:///home/user/project', name: 'My Project' },
+            { uri: 'file:///home/user/data', name: 'Data Directory' }
+        ]
+    };
+});
+```
+
+When the set of roots changes, notify the server so it can re-query:
+
+```typescript
+await client.sendRootsListChanged();
+```
+
+Root URIs must use the `file://` scheme. The `listChanged: true` capability flag is required to send change notifications.