feat(M8): implement MCP (Model Context Protocol) integration with stdio transport

Milestone M8 implementation adds MCP integration for connecting to external
tool servers and resources.

New crate: crates/integration/mcp-client
- JSON-RPC 2.0 protocol implementation
- Stdio transport for spawning MCP server processes
- Capability negotiation (initialize handshake)
- Tool operations:
  * tools/list: List available tools from server
  * tools/call: Invoke tools with arguments
- Resource operations:
  * resources/list: List available resources
  * resources/read: Read resource contents
- Async design using tokio for non-blocking I/O

MCP Client Features:
- McpClient: Main client with subprocess management
- ServerCapabilities: Capability discovery
- McpTool: Tool definitions with JSON schema
- McpResource: Resource definitions with URI/mime-type
- Automatic request ID management
- Error handling with proper JSON-RPC error codes

Permission Integration:
- Added Tool::Mcp to permission system
- Pattern matching support for mcp__server__tool format
  * "filesystem__*" matches all filesystem server tools
  * "filesystem__read_file" matches specific tool
- MCP requires Ask permission in Plan/AcceptEdits modes
- MCP allowed in Code mode (like Bash)

Tests added (3 new tests with mock Python servers):
1. mcp_server_capability_negotiation - Verifies initialize handshake
2. mcp_tool_invocation - Tests tool listing and calling
3. mcp_resource_reads - Tests resource listing and reading

Permission tests added (2 new tests):
1. mcp_server_pattern_matching - Verifies server-level wildcards
2. mcp_exact_tool_matching - Verifies tool-level exact matching

All 75 tests passing (up from 68).

Note: CLI integration deferred - MCP infrastructure is in place and fully
tested. Future work will add MCP server configuration and CLI commands to
invoke MCP tools.

Protocol: Implements MCP 2024-11-05 specification over stdio transport.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
2025-11-01 20:15:39 +01:00
parent b1b95a4560
commit 688d1fe58a
5 changed files with 665 additions and 1 deletions

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use mcp_client::McpClient;
use std::fs;
use tempfile::tempdir;
#[tokio::test]
async fn mcp_server_capability_negotiation() {
// Create a mock MCP server script
let dir = tempdir().unwrap();
let server_script = dir.path().join("mock_server.py");
let script_content = r#"#!/usr/bin/env python3
import sys
import json
def read_request():
line = sys.stdin.readline()
return json.loads(line)
def send_response(response):
sys.stdout.write(json.dumps(response) + '\n')
sys.stdout.flush()
# Main loop
while True:
try:
req = read_request()
method = req.get('method')
req_id = req.get('id')
if method == 'initialize':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'protocolVersion': '2024-11-05',
'capabilities': {
'tools': {'list_changed': True},
'resources': {'subscribe': False}
},
'serverInfo': {
'name': 'test-server',
'version': '1.0.0'
}
}
})
elif method == 'tools/list':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'tools': []
}
})
else:
send_response({
'jsonrpc': '2.0',
'id': req_id,
'error': {
'code': -32601,
'message': f'Method not found: {method}'
}
})
except EOFError:
break
except Exception as e:
sys.stderr.write(f'Error: {e}\n')
break
"#;
fs::write(&server_script, script_content).unwrap();
#[cfg(unix)]
{
use std::os::unix::fs::PermissionsExt;
fs::set_permissions(&server_script, std::fs::Permissions::from_mode(0o755)).unwrap();
}
// Connect to the server
let client = McpClient::spawn(
"python3",
&[server_script.to_str().unwrap()],
"test-server"
).await.unwrap();
// Initialize
let capabilities = client.initialize().await.unwrap();
// Verify capabilities
assert!(capabilities.tools.is_some());
assert_eq!(capabilities.tools.unwrap().list_changed, Some(true));
client.close().await.unwrap();
}
#[tokio::test]
async fn mcp_tool_invocation() {
let dir = tempdir().unwrap();
let server_script = dir.path().join("mock_server.py");
let script_content = r#"#!/usr/bin/env python3
import sys
import json
def read_request():
line = sys.stdin.readline()
return json.loads(line)
def send_response(response):
sys.stdout.write(json.dumps(response) + '\n')
sys.stdout.flush()
while True:
try:
req = read_request()
method = req.get('method')
req_id = req.get('id')
params = req.get('params', {})
if method == 'initialize':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'protocolVersion': '2024-11-05',
'capabilities': {
'tools': {}
},
'serverInfo': {
'name': 'test-server',
'version': '1.0.0'
}
}
})
elif method == 'tools/list':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'tools': [
{
'name': 'echo',
'description': 'Echo the input',
'input_schema': {
'type': 'object',
'properties': {
'message': {'type': 'string'}
}
}
}
]
}
})
elif method == 'tools/call':
tool_name = params.get('name')
arguments = params.get('arguments', {})
if tool_name == 'echo':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'content': [
{
'type': 'text',
'text': arguments.get('message', '')
}
]
}
})
else:
send_response({
'jsonrpc': '2.0',
'id': req_id,
'error': {
'code': -32602,
'message': f'Unknown tool: {tool_name}'
}
})
else:
send_response({
'jsonrpc': '2.0',
'id': req_id,
'error': {
'code': -32601,
'message': f'Method not found: {method}'
}
})
except EOFError:
break
except Exception as e:
sys.stderr.write(f'Error: {e}\n')
break
"#;
fs::write(&server_script, script_content).unwrap();
#[cfg(unix)]
{
use std::os::unix::fs::PermissionsExt;
fs::set_permissions(&server_script, std::fs::Permissions::from_mode(0o755)).unwrap();
}
let client = McpClient::spawn(
"python3",
&[server_script.to_str().unwrap()],
"test-server"
).await.unwrap();
client.initialize().await.unwrap();
// List tools
let tools = client.list_tools().await.unwrap();
assert_eq!(tools.len(), 1);
assert_eq!(tools[0].name, "echo");
// Call tool
let result = client.call_tool(
"echo",
serde_json::json!({"message": "Hello, MCP!"})
).await.unwrap();
// Verify result
let content = result.as_array().unwrap();
assert_eq!(content[0]["text"].as_str().unwrap(), "Hello, MCP!");
client.close().await.unwrap();
}
#[tokio::test]
async fn mcp_resource_reads() {
let dir = tempdir().unwrap();
let server_script = dir.path().join("mock_server.py");
let script_content = r#"#!/usr/bin/env python3
import sys
import json
def read_request():
line = sys.stdin.readline()
return json.loads(line)
def send_response(response):
sys.stdout.write(json.dumps(response) + '\n')
sys.stdout.flush()
while True:
try:
req = read_request()
method = req.get('method')
req_id = req.get('id')
params = req.get('params', {})
if method == 'initialize':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'protocolVersion': '2024-11-05',
'capabilities': {
'resources': {}
},
'serverInfo': {
'name': 'test-server',
'version': '1.0.0'
}
}
})
elif method == 'resources/list':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'resources': [
{
'uri': 'file:///test.txt',
'name': 'Test File',
'description': 'A test file',
'mime_type': 'text/plain'
}
]
}
})
elif method == 'resources/read':
uri = params.get('uri')
if uri == 'file:///test.txt':
send_response({
'jsonrpc': '2.0',
'id': req_id,
'result': {
'contents': [
{
'uri': uri,
'mime_type': 'text/plain',
'text': 'Hello from resource!'
}
]
}
})
else:
send_response({
'jsonrpc': '2.0',
'id': req_id,
'error': {
'code': -32602,
'message': f'Unknown resource: {uri}'
}
})
else:
send_response({
'jsonrpc': '2.0',
'id': req_id,
'error': {
'code': -32601,
'message': f'Method not found: {method}'
}
})
except EOFError:
break
except Exception as e:
sys.stderr.write(f'Error: {e}\n')
break
"#;
fs::write(&server_script, script_content).unwrap();
#[cfg(unix)]
{
use std::os::unix::fs::PermissionsExt;
fs::set_permissions(&server_script, std::fs::Permissions::from_mode(0o755)).unwrap();
}
let client = McpClient::spawn(
"python3",
&[server_script.to_str().unwrap()],
"test-server"
).await.unwrap();
client.initialize().await.unwrap();
// List resources
let resources = client.list_resources().await.unwrap();
assert_eq!(resources.len(), 1);
assert_eq!(resources[0].uri, "file:///test.txt");
// Read resource
let contents = client.read_resource("file:///test.txt").await.unwrap();
let contents_array = contents.as_array().unwrap();
assert_eq!(contents_array[0]["text"].as_str().unwrap(), "Hello from resource!");
client.close().await.unwrap();
}