MCP Protocol: The Bridge Between Agents and Tools

Overview

The Model Context Protocol (MCP) is the standard way for agents to discover, access, and use tools.

It solves a fundamental problem: how do we let agents safely use any tool or resource?

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What is MCP?

The Problem MCP Solves

# Without MCP (chaotic):
agent = Agent()
agent.tools = [
    GoogleSearchAPI(),
    GitHubAPI(),
    SlackAPI(),
    CustomDatabase(),
    FileSystem(),
    # ... each with different interfaces
]

# Each tool has different error handling, auth, rate limiting
# Agent must know about all of them
# Hard to add new tools
# Difficult to sandbox


# With MCP (standardized):
mcp_server = MCPServer()
mcp_server.register_resource('web_search', GoogleSearchAPI())
mcp_server.register_resource('github', GitHubAPI())
mcp_server.register_resource('slack', SlackAPI())

agent.connect_to_mcp(mcp_server)
# Agent discovers tools automatically
# Unified interface for all resources
# Easy to sandbox and control

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MCP Architecture

Request/Response Pattern

class MCPServer:
    """MCP Server that agents connect to"""

    def __init__(self):
        self.resources = {}
        self.tools = {}

    def register_tool(self, name: str, tool):
        """Register a tool with the server"""

        tool_definition = {
            'name': name,
            'description': tool.description,
            'inputSchema': {
                'type': 'object',
                'properties': tool.input_params,
                'required': tool.required_params
            }
        }

        self.tools[name] = tool_definition

    def handle_call_tool(self, name: str, arguments: dict):
        """Execute tool call"""

        if name not in self.tools:
            return {'error': f'Tool {name} not found'}

        tool = self.tools[name]['impl']

        try:
            result = tool(**arguments)
            return {'result': result, 'success': True}
        except Exception as e:
            return {'error': str(e), 'success': False}

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Tool Discovery

Automatic Tool Advertisement

class MCPClient:
    """Agent side: MCP Client"""

    def discover_tools(self):
        """Ask MCP server what tools are available"""

        # Send request to MCP server
        request = {
            'jsonrpc': '2.0',
            'id': 1,
            'method': 'tools/list',
            'params': {}
        }

        response = self.send_request(request)

        # Server responds with all available tools
        available_tools = response['result']['tools']

        # Agent now knows what it can do
        for tool in available_tools:
            self.register_available_tool(tool)

        return available_tools

    def use_tool(self, tool_name: str, args: dict):
        """Call a tool through MCP"""

        request = {
            'jsonrpc': '2.0',
            'id': 2,
            'method': 'tools/call',
            'params': {
                'name': tool_name,
                'arguments': args
            }
        }

        response = self.send_request(request)
        return response['result']

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Real-World Integrations

Google Drive + MCP

class GoogleDriveMCP:
    """MCP integration for Google Drive"""

    def __init__(self, credentials):
        self.drive = GoogleDriveService(credentials)

    def register_with_mcp(self, server):
        """Register all Drive operations"""

        server.register_tool('list_files', self.list_files)
        server.register_tool('read_file', self.read_file)
        server.register_tool('write_file', self.write_file)
        server.register_tool('delete_file', self.delete_file)
        server.register_tool('search_files', self.search_files)

    def list_files(self, folder_id: str = None):
        """List files in folder"""
        results = self.drive.files().list(
            q=f"'{folder_id}' in parents" if folder_id else None
        ).execute()
        return results['files']

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Security Model

Sandboxing Tools

class SecureMCPServer:
    """MCP server with security"""

    def __init__(self):
        self.permissions = {}  # User → allowed tools

    def authorize_tool_call(self, user_id: str, tool_name: str):
        """Check if user can call tool"""

        if user_id not in self.permissions:
            return False

        allowed_tools = self.permissions[user_id]
        return tool_name in allowed_tools

    def handle_call_with_auth(self, user_id: str, tool_name: str, args: dict):
        """Secure tool execution"""

        # Check permission
        if not self.authorize_tool_call(user_id, tool_name):
            return {'error': 'Permission denied'}

        # Rate limit
        if self.exceeded_rate_limit(user_id, tool_name):
            return {'error': 'Rate limit exceeded'}

        # Execute
        result = self.execute_tool(tool_name, args)

        # Audit log
        self.log_access(user_id, tool_name, result)

        return result

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3 Warnings ⚠️

Warning 1: Tool Explosion

# ❌ WRONG
# Register 100 tools with agent
for tool in all_available_tools:
    register(tool)

# Agent overwhelmed, can't choose
# Tokens wasted listing tools

# ✅ RIGHT
# Register only relevant tools
relevant_tools = filter_tools_by_capability(user_capability)
for tool in relevant_tools:
    register(tool)

# Agent focused on what it needs

Warning 2: No Rate Limiting

# ❌ WRONG
agent = Agent()
agent.can_call_tools()
# No rate limiting!
# Agent hammers API

# ✅ RIGHT
secure_server = SecureMCPServer()
secure_server.set_rate_limit('user_1', 'search', 100_per_hour)
agent.connect_to_secure_server(secure_server)

Warning 3: Leaking Tool Results

# ❌ WRONG
result = agent.call_tool()
return result  # Full output to client

# Might expose sensitive data

# ✅ RIGHT
result = agent.call_tool()
sanitized = sanitize_output(result)
return sanitized

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Last Updated: August 9, 2026