Add optional stateless MCP server for the real browser

Expose a conservative browser-cli tool surface to MCP hosts without
duplicating browser-control logic: every tool is a thin adapter over the
existing Python SDK, and each call builds a fresh BrowserCLI so the real
browser stays the only owner of tab and navigation state.

The MCP process resolves BROWSER_CLI_PROFILE, BROWSER_CLI_REMOTE, and
BROWSER_CLI_KEY explicitly instead of passing None down, so a pinned server
targets one browser rather than fanning listing calls out across every
connected browser. Explicit tool arguments still win.

Tool names keep a browser_ prefix for hosts that expose raw MCP names, while
BROWSER_CLI_MCP_TOOL_PREFIX lets hosts that already namespace by server drop
it and avoid names like browser_cli_testing_browser_tabs_list.

JavaScript evaluation, raw commands, storage writes, and session import stay
unexposed, and Streamable HTTP refuses non-loopback binds because the endpoint
has no authentication of its own; remote browsers go through browser-cli's
authenticated remote transport instead.

MCP stays an optional extra, so normal installs are unaffected.

README.md

@@ -70,6 +70,11 @@ For better remote-response compression, install the optional `fast` extra:
 uv tool install "real-browser-cli[fast]"
 ```
 
+To expose the conservative MCP tool surface, install the optional `mcp` extra:
+```sh
+uv tool install "real-browser-cli[mcp]"
+```
+
 To upgrade later:
 
 ```sh
@@ -141,6 +146,84 @@ browser-cli/
 
 ---
 
+## Stateless MCP server
+The optional MCP adapter exposes a small, typed subset of the Python SDK for
+MCP hosts such as Claude Desktop, Claude Code, Cursor, or VS Code. It controls
+the same real browser; it does not launch a headless browser or duplicate the
+browser command implementation.
+
+Install and run the local stdio server:
+```sh
+uv tool install "real-browser-cli[mcp]"
+browser-cli-mcp
+```
+
+Example MCP host configuration:
+```json
+{
+  "mcpServers": {
+    "browser-cli": {
+      "command": "browser-cli-mcp"
+    }
+  }
+}
+```
+
+The server is stateless at the MCP layer. Every tool call creates a fresh
+`BrowserCLI` SDK client, and browser state remains in the real browser. Pass
+`browser`, `remote`, and `key` on a tool call when a specific local profile or
+authenticated browser-cli remote is required.
+
+Available tools:
+- `browser_tabs_list`, `browser_tabs_open`, `browser_tabs_close`
+- `browser_navigate`, `browser_page_info`
+- `browser_extract_text`, `browser_extract_markdown`
+- `browser_dom_query`, `browser_dom_click`, `browser_dom_type`
+- `browser_screenshot`
+
+Generic JavaScript evaluation, raw browser commands, storage writes, and
+session import are intentionally not exposed.
+
+### Pinning one browser and naming tools
+Set `BROWSER_CLI_PROFILE` to pin every call from an MCP server to one browser,
+so tools do not have to pass `browser` and listing tools do not fan out across
+all connected browsers:
+```json
+{
+  "mcpServers": {
+    "browser-cli-testing": {
+      "command": "browser-cli-mcp",
+      "env": {
+        "BROWSER_CLI_PROFILE": "testing",
+        "BROWSER_CLI_MCP_TOOL_PREFIX": ""
+      }
+    }
+  }
+}
+```
+`BROWSER_CLI_REMOTE` and `BROWSER_CLI_KEY` pin an authenticated remote the same
+way. Explicit `browser`, `remote`, and `key` tool arguments still win.
+
+Tool names carry a `browser_` prefix by default so they stay unambiguous in
+hosts that expose raw MCP tool names. Hosts that already prefix tools with the
+server name produce stutter such as `browser_cli_testing_browser_tabs_list`;
+setting `BROWSER_CLI_MCP_TOOL_PREFIX` to an empty string drops the built-in
+prefix and yields `browser_cli_testing_tabs_list`. Any other value replaces the
+prefix.
+
+For local development and testing, Streamable HTTP is also available:
+```sh
+browser-cli-mcp --transport streamable-http --port 8000
+# endpoint: http://127.0.0.1:8000/mcp
+```
+
+HTTP uses stateless JSON responses and intentionally refuses non-loopback bind
+addresses because this MCP endpoint has no independent authentication. For a
+browser on another machine, keep MCP local and pass an authenticated
+browser-cli `remote` target to each tool call.
+
+---
+
 ## CLI reference
 During source development, commands are usually run as `uv run browser-cli [--browser ALIAS] <command>`. After tool installation, use `browser-cli ...` directly. Add `--remote HOST[:PORT]` and optionally `--key PATH` to target a browser exposed by `browser-cli serve`.