# MCP Server Refactoring Summary

## Changes Made

Refactored the MCP server implementation to follow the latest best practices from the official MCP documentation at https://modelcontextprotocol.io/docs/develop/build-server.

## Key Improvements

### 1. **Moved to Commands Directory**
- **Old**: `src/ctxai/mcp_server.py`
- **New**: `src/ctxai/commands/server_command.py`
- **Benefit**: Consistent with other commands (index_command.py, query_command.py, dashboard_command.py)

### 2. **Adopted FastMCP Framework**
- **Old**: Manual server creation with low-level MCP SDK
- **New**: FastMCP with decorator-based tool registration
- **Benefits**:
  - Automatic tool schema generation from type hints
  - Simpler, more pythonic code
  - Less boilerplate
  - Better type safety

### 3. **Proper Logging**
- **Added**: Stderr-based logging (not stdout)
- **Benefit**: Follows MCP best practice - stdout would corrupt JSON-RPC messages
- **Implementation**:
  ```python
  logging.basicConfig(
      level=logging.INFO,
      handlers=[logging.StreamHandler()]  # Uses stderr
  )
  console = Console(stderr=True)  # Rich also uses stderr
  ```

### 4. **Simplified Tool Registration**

#### Old Approach (Manual):
```python
@server.list_tools()
async def list_tools() -> list[Tool]:
    return [
        Tool(
            name="list_indexes",
            description="...",
            inputSchema={...}
        ),
        # ... more tools
    ]

@server.call_tool()
async def call_tool(name: str, arguments: Any):
    if name == "list_indexes":
        return await handle_list_indexes()
    # ... more handlers
```

#### New Approach (FastMCP):
```python
@mcp.tool()
async def list_indexes() -> str:
    """
    List all available code indexes with their statistics.
    
    Returns:
        String containing list of indexes
    """
    # Implementation here
```

**Benefits**:
- Tool name derived from function name
- Parameters derived from function signature
- Docstring becomes tool description
- Return type automatically handled
- No manual schema definition needed

### 5. **Better Error Handling**
- All tools return strings (not TextContent objects)
- FastMCP handles conversion automatically
- Errors logged to stderr with full traceback
- User-friendly error messages returned

### 6. **Updated Function Signatures**

Tools now use direct parameters instead of dictionary arguments:

#### Old:
```python
async def handle_query_codebase(arguments: dict, project_path):
    index_name = arguments["index_name"]
    query = arguments["query"]
    n_results = arguments.get("n_results", 5)
```

#### New:
```python
@mcp.tool()
async def query_codebase(
    index_name: str,
    query: str,
    n_results: int = 5
) -> str:
```

**Benefits**:
- Type hints for parameters
- Default values in signature
- IDE auto-completion
- Better documentation

## Code Statistics

### Before:
- **File**: `src/ctxai/mcp_server.py`
- **Lines**: ~367 lines
- **Approach**: Low-level MCP SDK
- **Tool registration**: Manual with schemas

### After:
- **File**: `src/ctxai/commands/server_command.py`
- **Lines**: ~283 lines (23% reduction)
- **Approach**: FastMCP framework
- **Tool registration**: Decorator-based

## Testing Updates

Updated tests to work with new structure:
- Changed imports from `ctxai.mcp_server` to `ctxai.commands.server_command`
- Updated to test `create_server()` instead of `create_mcp_server()`
- Simplified tests with FastMCP's cleaner API

## Documentation Updates

### MCP_SERVER.md
- Added note about FastMCP framework
- Included logging best practices section
- Updated architecture diagram
- Added code examples showing proper stderr usage

### Code Documentation
- All tools have comprehensive docstrings
- Type hints throughout
- Clear parameter descriptions
- Return value documentation

## Migration Notes

### No Breaking Changes
- CLI command unchanged: `ctxai server`
- Configuration unchanged
- Claude Desktop config unchanged
- All tools work exactly the same

### For Developers
- New pattern for adding tools (use `@mcp.tool()` decorator)
- Automatic schema generation from type hints
- Must use stderr for logging (never stdout)

## Best Practices Adopted

From https://modelcontextprotocol.io/docs/develop/build-server:

### ✅ Implemented:
1. **FastMCP Framework**: Modern, decorator-based approach
2. **Stderr Logging**: Never write to stdout
3. **Type Hints**: Automatic schema generation
4. **Async/Await**: Non-blocking operations
5. **Docstrings**: Auto-converted to tool descriptions
6. **Error Handling**: Graceful failures
7. **Transport**: stdio mode for Claude Desktop

### 📚 Documentation:
1. Clear tool descriptions
2. Parameter documentation
3. Usage examples
4. Troubleshooting guide

## Example: Before and After

### Adding a New Tool

#### Before (Manual Schema):
```python
@server.list_tools()
async def list_tools() -> list[Tool]:
    return [
        # ... existing tools,
        Tool(
            name="new_tool",
            description="Does something useful",
            inputSchema={
                "type": "object",
                "properties": {
                    "param1": {
                        "type": "string",
                        "description": "First parameter"
                    },
                    "param2": {
                        "type": "integer",
                        "description": "Second parameter",
                        "default": 10
                    }
                },
                "required": ["param1"]
            }
        )
    ]

@server.call_tool()
async def call_tool(name: str, arguments: Any):
    if name == "new_tool":
        return await handle_new_tool(arguments)
    # ... other tools

async def handle_new_tool(arguments: dict):
    param1 = arguments["param1"]
    param2 = arguments.get("param2", 10)
    # Implementation
    return [TextContent(type="text", text="Result")]
```

#### After (FastMCP):
```python
@mcp.tool()
async def new_tool(param1: str, param2: int = 10) -> str:
    """
    Does something useful.
    
    Args:
        param1: First parameter
        param2: Second parameter (default: 10)
    
    Returns:
        Result string
    """
    # Implementation
    return "Result"
```

**Lines of code**:
- Before: ~40 lines
- After: ~12 lines
- **Reduction: 70%**

## Performance

No performance impact:
- FastMCP is a thin wrapper over MCP SDK
- Same underlying protocol
- Same async/await architecture
- Same stdio communication

## Security

No security changes:
- Same stdio isolation
- Same process-level security
- Logging to stderr doesn't expose data
- No additional network exposure

## Future Enhancements

FastMCP enables easier additions:

### Resources (Future):
```python
@mcp.resource("file://code/{path}")
async def read_code_file(path: str) -> str:
    """Read a specific code file."""
    # Implementation
```

### Prompts (Future):
```python
@mcp.prompt()
async def review_code(file: str) -> str:
    """Generate code review prompt."""
    # Implementation
```

## Conclusion

The refactoring successfully modernizes the MCP server implementation:

1. ✅ **Follows Official Best Practices**: Uses recommended FastMCP framework
2. ✅ **Cleaner Code**: 23% reduction in lines of code
3. ✅ **Better Maintainability**: Decorator-based is more intuitive
4. ✅ **Type Safe**: Automatic schema generation from type hints
5. ✅ **No Breaking Changes**: Same API, same behavior
6. ✅ **Proper Logging**: Stderr only (stdio-safe)
7. ✅ **Well Documented**: Updated docs with examples

The server is now production-ready and follows modern MCP development patterns.
