docs: document MCP-backed dynamic tool discovery feature

Update README.md to document the new MCP-backed fetch_tools() capability,
highlighting the dynamic tool discovery feature that allows runtime updates
without SDK releases.

Changes:
- Added feature highlight: "Dynamic MCP-backed discovery via fetch_tools()"
- Added installation note for optional MCP dependencies
- Clarified that fetch_tools() uses StackOne MCP server under the hood
- Noted Python 3.10+ requirement for MCP functionality

This brings the Python SDK documentation in line with the Node SDK's
MCP feature documentation.

Author: ryoppippi

README.md

@@ -14,6 +14,7 @@ StackOne AI provides a unified interface for accessing various SaaS tools throug
   - Glob pattern filtering with patterns like `"hris_*"` and exclusions `"!hris_delete_*"`
   - Provider and action filtering with `fetch_tools()`
   - Multi-account support
+- Dynamic MCP-backed discovery via `fetch_tools()` so you can pull the latest tools at runtime (accounts, providers, or globbed actions)
 - **Meta Tools** (Beta): Dynamic tool discovery and execution based on natural language queries using hybrid BM25 + TF-IDF search
 - Integration with popular AI frameworks:
   - OpenAI Functions
@@ -105,6 +106,8 @@ tools = toolset.get_tools(["hris_*", "!hris_delete_*"])
 
 The `fetch_tools()` method provides advanced filtering by providers, actions, and account IDs:
 
+> `fetch_tools()` uses the StackOne MCP server under the hood. Install the optional extra (`pip install 'stackone-ai[mcp]'`) on Python 3.10+ to enable dynamic discovery.
+
 ```python
 from stackone_ai import StackOneToolSet