#!/usr/bin/env python3
"""
Basic MCP Server: Read/Write Disk Files
A minimal MCP server with only read and write file operations.
"""
import asyncio
from pathlib import Path
from mcp.server import Server
from mcp.server.stdio import stdio_server
from mcp.types import (
Tool,
TextContent,
CallToolResult,
ListToolsResult,
)
# Initialize the MCP server
app = Server("basic-fileserver")
# Default sandbox directory for file operations
SANDBOX_DIR = Path("sandbox")
SANDBOX_DIR.mkdir(exist_ok=True)
def resolve_sandbox_path(path_str: str) -> Path:
"""Resolve a path relative to the sandbox directory."""
path = Path(path_str)
# If path is absolute, use it as-is (for safety, still resolve relative to sandbox)
# Otherwise, resolve relative to sandbox
if path.is_absolute():
# For absolute paths, still constrain to sandbox for security
return SANDBOX_DIR / path.name
return SANDBOX_DIR / path
async def read_file_tool(arguments: dict) -> CallToolResult:
"""Read and return the contents of a file from the sandbox directory."""
path = resolve_sandbox_path(arguments["path"])
if not path.is_file():
return CallToolResult(
content=[TextContent(type="text", text=f"Error: Not a file - {path}")],
isError=True,
)
try:
contents = path.read_text(encoding="utf-8")
except Exception as e:
return CallToolResult(
content=[TextContent(type="text", text=f"Error reading file: {e}")],
isError=True,
)
return CallToolResult(
content=[TextContent(type="text", text=contents)]
)
async def write_file_tool(arguments: dict) -> CallToolResult:
"""Write string content to a file in the sandbox directory."""
path = resolve_sandbox_path(arguments["path"])
content = arguments["content"]
try:
path.parent.mkdir(parents=True, exist_ok=True)
path.write_text(content, encoding="utf-8")
except Exception as e:
return CallToolResult(
content=[TextContent(type="text", text=f"Error writing file: {e}")],
isError=True,
)
return CallToolResult(
content=[TextContent(type="text", text=f"Successfully wrote to {path}")]
)
@app.list_tools()
async def list_tools() -> ListToolsResult:
"""List all available file tools."""
return ListToolsResult(
tools=[
Tool(
name="read_file",
description="Read and return the contents of a file from the sandbox directory.",
inputSchema={
"type": "object",
"properties": {
"path": {
"type": "string",
"description": "The path to the file (relative to sandbox directory)",
}
},
"required": ["path"],
},
),
Tool(
name="write_file",
description="Write string content to a file in the sandbox directory.",
inputSchema={
"type": "object",
"properties": {
"path": {
"type": "string",
"description": "The target file path (relative to sandbox directory)",
},
"content": {
"type": "string",
"description": "The content to write",
},
},
"required": ["path", "content"],
},
),
]
)
@app.call_tool()
async def call_tool(name: str, arguments: dict) -> CallToolResult:
"""Handle tool calls and route to appropriate handler."""
if name == "read_file":
return await read_file_tool(arguments)
elif name == "write_file":
return await write_file_tool(arguments)
else:
return CallToolResult(
content=[TextContent(type="text", text=f"Unknown tool: {name}")],
isError=True,
)
async def main():
async with stdio_server() as (read_stream, write_stream):
await app.run(
read_stream,
write_stream,
app.create_initialization_options()
)
if __name__ == "__main__":
asyncio.run(main())
