Add MCP support

aider/args.py

@@ -543,6 +543,62 @@ def get_parser(default_config_files, git_root):
         default=False,
     )
 
+    #########
+    group = parser.add_argument_group("Model Context Protocol (MCP)")
+    group.add_argument(
+        "--mcp",
+        action=argparse.BooleanOptionalAction,
+        default=False,
+        help="Enable/disable Model Context Protocol (MCP) support (default: False)",
+    )
+    group.add_argument(
+        "--mcp-servers",
+        action="append",
+        metavar="SERVER_NAME",
+        help="Specify MCP server names to enable (can be used multiple times)",
+        default=[],
+    )
+    group.add_argument(
+        "--mcp-server-command",
+        action="append",
+        metavar="SERVER_NAME:COMMAND",
+        help="Specify the command to execute for an MCP server (can be used multiple times)",
+        default=[],
+    )
+
+    group.add_argument(
+        "--mcp-server-env",
+        action="append",
+        metavar="SERVER_NAME:ENV_VAR=VALUE",
+        help="Specify environment variables for an MCP server (can be used multiple times)",
+        default=[],
+    )
+    group.add_argument(
+        "--mcp-tool-permission",
+        action="append",
+        metavar="SERVER_NAME:TOOL_NAME=PERMISSION",
+        help="Specify permission ('manual' or 'auto') for an MCP tool (can be used multiple times)",
+        default=[],
+    )
+    group.add_argument(
+        "--list-mcp-servers",
+        action="store_true",
+        help="List all configured MCP servers and exit",
+        default=False,
+    )
+    group.add_argument(
+        "--list-mcp-tools",
+        action="store_true",
+        help="List all available MCP tools and exit",
+        default=False,
+    )
+    group.add_argument(
+        "--mcp-wait-for-stdio",
+        action=argparse.BooleanOptionalAction,
+        default=False,
+        help="Wait for STDIO MCP clients to complete tool discovery (default: False)",
+    )
+
     #########
     group = parser.add_argument_group("Upgrading")
     group.add_argument(

aider/coders/base_coder.py

@@ -17,9 +17,10 @@
 from datetime import datetime
 from json.decoder import JSONDecodeError
 from pathlib import Path
-from typing import List
+from typing import List, Optional, Tuple
 
 from aider import __version__, models, prompts, urls, utils
+from aider.mcp import is_mcp_enabled, get_available_tools_prompt, process_llm_tool_requests, stop_mcp_servers
 from aider.analytics import Analytics
 from aider.commands import Commands
 from aider.exceptions import LiteLLMExceptions
@@ -957,6 +958,7 @@ def keyboard_interrupt(self):
         if self.last_keyboard_interrupt and now - self.last_keyboard_interrupt < thresh:
             self.io.tool_warning("\n\n^C KeyboardInterrupt")
             self.event("exit", reason="Control-C")
+            stop_mcp_servers()
             sys.exit()
 
         self.io.tool_warning("\n\n^C again to exit")
@@ -1106,6 +1108,11 @@ def fmt_system_prompt(self, prompt):
             )
         else:
             quad_backtick_reminder = ""
+
+        # Add MCP tools information if MCP is enabled
+        mcp_tools_info = ""
+        if is_mcp_enabled():
+            mcp_tools_info = self.gpt_prompts.mcp_tools_prefix + "\n\n" + get_available_tools_prompt()
 
         prompt = prompt.format(
             fence=self.fence,
@@ -1119,6 +1126,10 @@ def fmt_system_prompt(self, prompt):
 
         if self.main_model.system_prompt_prefix:
             prompt = self.main_model.system_prompt_prefix + prompt
+
+        # Append MCP tools information to the end of the prompt
+        if mcp_tools_info:
+            prompt += "\n\n" + mcp_tools_info
 
         return prompt
 
@@ -1455,6 +1466,14 @@ def send_message(self, inp):
                     self.reflected_message = add_rel_files_message
                 return
 
+            tool_results = self.check_for_tool_calls(content)
+            for tool_result in tool_results:
+                if self.reflected_message:
+                    self.reflected_message += "\n\n" + tool_result
+                else:
+                    self.reflected_message = tool_result
+                return
+
             try:
                 if self.reply_completed():
                     return
@@ -1647,6 +1666,13 @@ def get_file_mentions(self, content, ignore_current=False):
 
         return mentioned_rel_fnames
 
+    def check_for_tool_calls(self, content):
+        """Process the LLM's response after it's completed."""
+        if is_mcp_enabled():
+            return process_llm_tool_requests(content, self.io)
+        else:
+            return []
+
     def check_for_file_mentions(self, content):
         mentioned_rel_fnames = self.get_file_mentions(content)
 

aider/coders/base_prompts.py

@@ -1,5 +1,25 @@
 class CoderPrompts:
     system_reminder = ""
+
+    mcp_tools_prefix = """# MCP Tools
+
+You can use Model Context Protocol (MCP) tools to interact with external systems. To use a tool, include a tool execution request in your response using the following format:
+
+```
+<use_mcp_tool>
+<server_name>server name here</server_name>
+<tool_name>tool name here</tool_name>
+<arguments>
+{
+  "param1": "value1",
+  "param2": "value2"
+}
+</arguments>
+</use_mcp_tool>
+```
+
+The available tools will be listed below if any are connected.
+"""
 
     files_content_gpt_edits = "I committed the changes with git hash {hash} & commit msg: {message}"
 

aider/commands.py

@@ -2,6 +2,7 @@
 import os
 import re
 import subprocess
+import json
 import sys
 import tempfile
 from collections import OrderedDict
@@ -13,6 +14,7 @@
 from prompt_toolkit.completion import Completion, PathCompleter
 from prompt_toolkit.document import Document
 
+from aider.mcp import list_mcp_servers, list_mcp_tools, execute_mcp_tool, stop_mcp_servers
 from aider import models, prompts, voice
 from aider.editor import pipe_editor
 from aider.format_settings import format_settings
@@ -1009,6 +1011,7 @@ def cmd_run(self, args, add_on_nonzero_exit=False):
 
     def cmd_exit(self, args):
         "Exit the application"
+        stop_mcp_servers()
         self.coder.event("exit", reason="/exit")
         sys.exit()
 
@@ -1542,6 +1545,78 @@ def cmd_reasoning_effort(self, args):
         announcements = "\n".join(self.coder.get_announcements())
         self.io.tool_output(announcements)
 
+    def cmd_mcp_servers(self, args):
+        "List all configured MCP servers"
+        servers = list_mcp_servers()
+        if servers:
+            self.io.tool_output("Configured MCP servers:")
+            for server in servers:
+                status = "Enabled" if server.enabled else "Disabled"
+                self.io.tool_output(f"  - {server.name} ({status})")
+                if server.command:
+                    self.io.tool_output(f"    Command: {server.command}")
+                if server.env_vars:
+                    self.io.tool_output("    Environment variables:")
+                    for var, value in server.env_vars.items():
+                        masked_value = "*" * len(value) if value else "(empty)"
+                        self.io.tool_output(f"      {var}={masked_value}")
+        else:
+            self.io.tool_output("No MCP servers configured.")
+
+    def cmd_mcp_tools(self, args):
+        "List all available MCP tools, optionally filtered by server name"
+        server_name = args.strip()
+        tools_by_server = list_mcp_tools()
+
+        if not tools_by_server:
+            self.io.tool_output("No MCP tools available.")
+            return
+
+        if server_name:
+            if server_name in tools_by_server:
+                self.io.tool_output(f"Tools for MCP server '{server_name}':")
+                for tool in tools_by_server[server_name]:
+                    self.io.tool_output(f"  - {tool.name} (Permission: {tool.permission})")
+                    if tool.description:
+                        self.io.tool_output(f"    Description: {tool.description}")
+            else:
+                self.io.tool_output(f"No MCP server found with name '{server_name}'.")
+        else:
+            self.io.tool_output("Available MCP tools:")
+            for server_name, tools in tools_by_server.items():
+                self.io.tool_output(f"  Server: {server_name}")
+                for tool in tools:
+                    self.io.tool_output(f"    - {tool.name} (Permission: {tool.permission})")
+                    if tool.description:
+                        self.io.tool_output(f"      Description: {tool.description}")
+
+    def cmd_mcp_execute(self, args):
+        "Execute an MCP tool with the given arguments"
+        # Parse the arguments
+        parts = args.strip().split(maxsplit=2)
+        if len(parts) < 2:
+            self.io.tool_error("Usage: /mcp-execute <server_name> <tool_name> [arguments_json]")
+            return
+
+        server_name, tool_name = parts[0], parts[1]
+        arguments = {}
+
+        if len(parts) > 2:
+            try:
+                arguments = json.loads(parts[2])
+            except json.JSONDecodeError:
+                self.io.tool_error(f"Invalid JSON arguments: {parts[2]}")
+                return
+
+        # Execute the tool
+        self.io.tool_output(f"Executing MCP tool '{tool_name}' from server '{server_name}'...")
+        try:
+            result = execute_mcp_tool(server_name, tool_name, arguments, self.io)
+            self.io.tool_output("Result:")
+            self.io.tool_output(result)
+        except Exception as e:
+            self.io.tool_error(f"Error executing MCP tool: {str(e)}")
+
     def cmd_copy_context(self, args=None):
         """Copy the current chat context as markdown, suitable to paste into a web UI"""
 

aider/main.py

@@ -8,6 +8,8 @@
 from dataclasses import fields
 from pathlib import Path
 
+from aider import mcp
+
 try:
     import git
 except ImportError:
@@ -714,6 +716,53 @@ def get_io(pretty):
     if args.check_update:
         check_version(io, verbose=args.verbose)
 
+    if args.list_models:
+        models.print_matching_models(io, args.list_models)
+        analytics.event("exit", reason="Listed models")
+        return 0
+
+    # Configure MCP manager
+    mcp.configure_mcp(args)
+
+    # Initialize MCP servers and discover tools
+    if mcp.is_mcp_enabled():
+        mcp.initialize_mcp_servers(io)
+
+    # Handle MCP-related commands
+    if args.list_mcp_servers:
+        servers = mcp.list_mcp_servers()
+        if servers:
+            io.tool_output("Configured MCP servers:")
+            for server in servers:
+                status = "Enabled" if server.enabled else "Disabled"
+                io.tool_output(f"  - {server.name} ({status})")
+                if server.command:
+                    io.tool_output(f"    Command: {server.command}")
+                if server.env_vars:
+                    io.tool_output("    Environment variables:")
+                    for var, value in server.env_vars.items():
+                        masked_value = "*" * len(value) if value else "(empty)"
+                        io.tool_output(f"      {var}={masked_value}")
+        else:
+            io.tool_output("No MCP servers configured.")
+        analytics.event("exit", reason="Listed MCP servers")
+        return 0
+
+    if args.list_mcp_tools:
+        tools_by_server = mcp.list_mcp_tools()
+        if tools_by_server:
+            io.tool_output("Available MCP tools:")
+            for server_name, tools in tools_by_server.items():
+                io.tool_output(f"  Server: {server_name}")
+                for tool in tools:
+                    io.tool_output(f"    - {tool.name} (Permission: {tool.permission})")
+                    if tool.description:
+                        io.tool_output(f"      Description: {tool.description}")
+        else:
+            io.tool_output("No MCP tools available.")
+        analytics.event("exit", reason="Listed MCP tools")
+        return 0
+
     if args.git:
         git_root = setup_git(git_root, io)
         if args.gitignore:
@@ -852,6 +901,7 @@ def get_io(pretty):
                 io.tool_output()
             except KeyboardInterrupt:
                 analytics.event("exit", reason="Keyboard interrupt during model warnings")
+                mcp.stop_mcp_servers()
                 return 1
 
     repo = None
@@ -1215,4 +1265,4 @@ def load_slow_imports(swallow=True):
 
 if __name__ == "__main__":
     status = main()
-    sys.exit(status)
+    sys.exit(status)