mcpcodeserver

A Model Context Protocol (MCP) proxy server that translates tool calls into TypeScript code generation. Instead of making multiple tool calls back and forth, LLMs can write TypeScript code that calls multiple tools naturally, reducing token overhead and leveraging the LLM's superior code generation capabilities.

❌ Without mcpcodeserver

LLMs make multiple sequential tool calls, burning tokens and struggling with complex workflows:

❌ Multiple round-trips between LLM and tools
❌ Complex tool calling sequences are error-prone
❌ Data cannot easily be passed between tools
❌ Limited error handling and control flow

✅ With mcpcodeserver

LLMs write TypeScript code that calls multiple tools naturally:

✅ Write code to call multiple tools in sequence
✅ Use variables, loops, and conditionals naturally
✅ Better error handling with try/catch
✅ Reduce token usage by combining operations
✅ Leverage LLM's strong code generation capabilities

Quick Start

Install mcpcodeserver in your MCP client (see installation section below)
Create an mcp.json configuration file with your child MCP servers
Start using it - your LLM can now generate and execute TypeScript code that calls your tools

// Instead of multiple tool calls, write code like this:
const files = await filesystem.list_directory({ path: "/tmp" });
const results = await Promise.all(
  files.map(file => filesystem.read_file({ path: file.path }))
);
return results.filter(content => content.includes("important"));

Overview

mcpcodeserver is a unique MCP server that:

Acts as an MCP client to connect to one or more child MCP servers
Discovers all tools from child servers
Exposes three powerful tools to parent LLM clients:
1. list_servers - Lists all available sub-servers connected to this MCP server
2. get_tool_definitions - Returns TypeScript type definitions for discovered tools (optionally filtered by server)
3. generate_and_execute_code - Generates and executes TypeScript code that calls those tools in a sandbox

This architecture allows LLMs to orchestrate complex multi-tool workflows by writing code instead of making sequential tool calls, which is often more efficient and natural for modern language models.

Related Work & Research

This approach is inspired by recent research showing that LLMs perform better when generating executable code rather than making direct tool calls:

CodeAct: Your LLM Agent Acts Better when Generating Code (Apple, ICML 2024) - Demonstrates that LLM agents achieve up to 20% higher success rates when using executable Python code as a unified action space instead of pre-defined tool calling formats.
Cloudflare Code Mode - A similar implementation that converts MCP tools into TypeScript APIs, showing that "LLMs are better at writing code to call MCP, than at calling MCP directly."

The key insight from this research is that LLMs have extensive training on real-world code but limited exposure to synthetic tool-calling formats, making code generation a more natural and effective approach for complex agent workflows.

Why Use This?

Traditional Tool Calling Problems

Multiple round-trips between LLM and tools burn tokens
LLMs often struggle with complex tool calling sequences
Each tool call requires JSON schema understanding and formatting
Data cannot easily be passed between tools without going through the LLM

Code Generation Solution

Write TypeScript code to call multiple tools in sequence
Use variables, loops, and conditionals naturally
Better error handling with try/catch
Reduce token usage by combining operations
Leverage LLM's strong code generation capabilities

Dynamic Tool Discovery

mcpcodeserver automatically monitors child MCP servers for tool changes and notifies parent clients when tools are added, removed, or modified:

Automatic Refresh: Checks for tool changes every 30 seconds
Real-time Notifications: Sends notifications/tools/list_changed to parent clients
Dynamic Updates: Tool definitions and summaries update automatically
No Manual Refresh: Parent LLMs receive notifications to refresh their tool knowledge

This ensures that parent LLMs always have the most current tool definitions without requiring manual intervention.

Server Filtering

To reduce context window usage and improve focus, mcpcodeserver supports filtering tool definitions by specific servers:

List Available Servers: Use list_servers to see all connected sub-servers
Filtered Tool Definitions: Use get_tool_definitions with server_names parameter to get tools from specific servers only
Reduced Verbosity: Get focused TypeScript definitions without overwhelming the LLM's context window
Method Namespacing: All generated functions are prefixed with server names (e.g., pizzashop_create_pizza, filesystem_read_file)

Example usage:

// List available servers
const servers = await list_servers({});
// Returns: ["pizzashop", "filesystem", "memory"]

// Get all tool definitions
const allTools = await get_tool_definitions({});

// Get only pizzashop tools
const pizzashopTools = await get_tool_definitions({
  server_names: ["pizzashop"]
});

Advanced MCP Features

mcpcodeserver supports pass-through of advanced MCP protocol features when both parent and child servers support them:

Elicitation: Child servers can request user input during tool execution, which is passed through to parent clients
Roots: Lists and aggregates roots from all child servers, providing a unified view of available resources
Sampling: Enables LLM sampling requests to be passed through to child servers for advanced AI capabilities

These features are automatically advertised to parent clients and work seamlessly when supported by the underlying child MCP servers.

Quick Start

Try it immediately with npx (no installation required):

# From GitHub
npx github:zbowling/mcpcodeserver --help

# Or when published to npm
npx mcpcodeserver --help

🛠️ Installation

Requirements

Node.js >= v18.0.0
Cursor, Claude Code, VSCode, Windsurf or another MCP Client

Installing via Smithery

To install mcpcodeserver for any client automatically via Smithery:

npx -y @smithery/cli@latest install mcpcodeserver --client <client-name> --key <smithery-key>

Install in Cursor

Go to: Settings -> Cursor Settings -> MCP -> Add new global MCP server

Pasting the following configuration into your Cursor ~/.cursor/mcp.json file is the recommended approach. You may also install in a specific project by creating .cursor/mcp.json in your project folder.

Cursor One-Click Installation

Cursor Local Server Connection

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Cursor Remote Server Connection (if you set up HTTP transport)

{
  "mcpServers": {
    "mcpcodeserver": {
      "url": "http://localhost:3000/mcp"
    }
  }
}

Install in Claude Code

Run this command. See Claude Code MCP docs for more info.

Claude Code Local Server Connection

claude mcp add mcpcodeserver -- npx -y mcpcodeserver --config /path/to/your/mcp.json

Claude Code Remote Server Connection

claude mcp add --transport http mcpcodeserver http://localhost:3000/mcp

Install in VSCode

VSCode One-Click Installation

VSCode Manual Configuration

Add to your VSCode MCP settings:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in Windsurf

Windsurf One-Click Installation

Install in AI Coding Assistants

For Continue, Cline, and RooCode, add to your configuration:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in Amp

Run this command in your terminal. See Amp MCP docs for more info.

amp mcp add mcpcodeserver -- npx -y mcpcodeserver --config /path/to/your/mcp.json

Install in Text Editors

For Aider, Codium, Zed, Nova, and Sublime Text, add to your configuration:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in Neovim

Add to your Neovim MCP configuration:

{
  mcpServers = {
    mcpcodeserver = {
      command = "npx",
      args = {"-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"}
    }
  }
}

Install in Emacs

Add to your Emacs MCP configuration:

(setq mcp-servers
      '((mcpcodeserver
         :command "npx"
         :args ("-y" "mcpcodeserver" "--config" "/path/to/your/mcp.json"))))

Install in JetBrains IDEs

For IntelliJ IDEA, WebStorm, PyCharm, and Android Studio, add to your MCP settings:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in AI Tools

For Codeium, Tabnine, GitHub Copilot, and Amazon CodeWhisperer, add to your MCP settings:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in Cloud IDEs

For Replit, CodeSandbox, StackBlitz, GitPod, GitHub Codespaces, GitLab Web IDE, and Bitbucket Cloud, add to your MCP settings:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in Other Tools

For Xcode, Fleet, Sourcegraph, and JetBrains Gateway, add to your MCP configuration:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Install in Remote Development

For remote development environments, you can also use HTTP transport:

{
  "mcpServers": {
    "mcpcodeserver": {
      "url": "http://your-server:3000/mcp"
    }
  }
}

Configuration File

Create an mcp.json configuration file to define your child MCP servers:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"],
      "env": { "DEBUG": "false" }
    },
    "memory": {
      "command": "npx", 
      "args": ["-y", "@modelcontextprotocol/server-memory"]
    },
    "brave-search": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-brave-search"],
      "env": { "BRAVE_API_KEY": "your-api-key" }
    }
  }
}

Installation for Development

# Install dependencies (using Bun for faster performance)
bun install

# Or with npm
npm install

# Build the project
bun run build

# Test the built server
bun dist/index.js --help

Note: This project uses Bun for better performance, but npm/node also work fine.

🚨 Troubleshooting

Module Not Found Errors

If you encounter ERR_MODULE_NOT_FOUND, try using bunx instead of npx:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "bunx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

ESM Resolution Issues

For errors like Error: Cannot find module, try the --experimental-vm-modules flag:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "--node-options=--experimental-vm-modules", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

TLS/Certificate Issues

Use the --experimental-fetch flag to bypass TLS-related problems:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "--node-options=--experimental-fetch", "mcpcodeserver", "--config", "/path/to/your/mcp.json"]
    }
  }
}

General MCP Client Errors

Try adding @latest to the package name
Use bunx as an alternative to npx
Consider using deno as another alternative
Ensure you're using Node.js v18 or higher for native fetch support

Configuration Issues

Make sure your mcp.json file is valid JSON
Check that all child server commands are available in your PATH
Verify that child servers can start independently
Check file permissions for the config file path

Testing with MCP Inspector

npx -y @modelcontextprotocol/inspector npx mcpcodeserver --config /path/to/your/mcp.json

💻 Development

CLI Arguments

mcpcodeserver accepts the following CLI flags:

--config <path> – Path to the MCP configuration file (default: ./mcp.json)
--transport <stdio|http> – Transport to use (stdio by default). Note that HTTP transport automatically provides both HTTP and SSE endpoints
--port <number> – Port to listen on when using http transport (default 3000)
--help – Show help message

Example with HTTP transport and port 8080:

npx mcpcodeserver --config /path/to/mcp.json --transport http --port 8080

Example with stdio transport:

npx mcpcodeserver --config /path/to/mcp.json --transport stdio

Environment Variables

You can use environment variables for configuration:

MCP_CONFIG_PATH – Path to the MCP configuration file (alternative to --config)
MCP_TRANSPORT – Transport type (alternative to --transport)
MCP_PORT – Port number for HTTP transport (alternative to --port)

Example with environment variables:

# .env
MCP_CONFIG_PATH=/path/to/your/mcp.json
MCP_TRANSPORT=stdio

Example MCP configuration using environment variables:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver"],
      "env": {
        "MCP_CONFIG_PATH": "/path/to/your/mcp.json"
      }
    }
  }
}

Note: CLI flags take precedence over environment variables when both are provided.

Local Development Configuration

For local development, you can run the TypeScript source directly:

{
  "mcpServers": {
    "mcpcodeserver": {
      "command": "npx",
      "args": ["tsx", "/path/to/mcpcodeserver/src/index.ts", "--config", "/path/to/your/mcp.json"]
    }
  }
}

Running Modes

Stdio Mode (Default)

The server runs in stdio mode by default, which is perfect for integration with MCP clients like Claude Desktop:

# Run in stdio mode
npx mcpcodeserver --config mcp.json

# Or with custom config path
npx mcpcodeserver --config /path/to/your/mcp.json

HTTP Mode

For debugging, testing, or integration with web-based MCP clients, you can run the server in HTTP mode:

# Run in HTTP mode on default port 3000
npx mcpcodeserver --http --config mcp.json

# Run on custom port and host
npx mcpcodeserver --http --port 8080 --host 0.0.0.0 --config mcp.json

When running in HTTP mode, the server will be available at:

Server URL: http://localhost:3000/mcp (or your custom host:port)
MCP Inspector: Use npx @modelcontextprotocol/inspector http://localhost:3000/mcp to debug and test

MCP Inspector Integration

The MCP Inspector is a powerful tool for debugging and testing MCP servers. When running in HTTP mode, you can use it to:

Inspect available tools and their schemas
Test tool calls interactively
Debug resource access and prompts
Monitor real-time notifications

# Start the server in HTTP mode
npx mcpcodeserver --http --config mcp.json

# In another terminal, start the MCP Inspector
npx @modelcontextprotocol/inspector http://localhost:3000/mcp

# Or use the shorthand script (includes all example servers)
npm run inspector

The inspector will open in your browser and provide a full interface for exploring and testing your MCP server.

Note: The npm run inspector command uses mcp-test.json which includes 8 MCP servers (67 tools total) from the official examples, including both TypeScript (npx) and Python (uvx) based servers.

Configuration

Create an mcp.json file that defines which child MCP servers to connect to. This follows the standard MCP client configuration format:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"],
      "env": {
        "DEBUG": "false"
      }
    },
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "your-token-here"
      }
    },
    "weather": {
      "url": "http://localhost:3000/mcp",
      "transport": "sse"
    }
  }
}

Configuration Options

Each server entry supports:

For stdio transport:

command (required) - The command to execute (e.g., "node", "python", "npx")
args (optional) - Array of arguments to pass to the command
env (optional) - Environment variables for the child process

For HTTP/SSE transport:

url (required) - The HTTP endpoint URL
transport - Set to "sse" for Server-Sent Events

Usage

Starting the Server

# Use default config (./mcp.json)
mcpcodeserver

# Use custom config location
mcpcodeserver --config /path/to/custom-mcp.json

# Show help
mcpcodeserver --help

Using as an MCP Server

Configure mcpcodeserver in your MCP client (like Claude Desktop, Claude Code, Cline, etc.):

With npx (recommended - no installation needed):

{
  "mcpServers": {
    "codeserver": {
      "command": "npx",
      "args": ["-y", "mcpcodeserver", "--config", "/path/to/mcp.json"]
    }
  }
}

From GitHub (works immediately):

{
  "mcpServers": {
    "codeserver": {
      "command": "npx",
      "args": ["-y", "github:zbowling/mcpcodeserver", "--config", "/path/to/mcp.json"]
    }
  }
}

With other package managers:

// yarn
{ "command": "yarn", "args": ["dlx", "mcpcodeserver", "--config", "/path/to/mcp.json"] }

// pnpm
{ "command": "pnpm", "args": ["dlx", "mcpcodeserver", "--config", "/path/to/mcp.json"] }

// bun
{ "command": "bunx", "args": ["mcpcodeserver", "--config", "/path/to/mcp.json"] }

See examples/ for more configuration examples and MCP client-specific setups.

Tool 1: get_tool_definitions

This tool returns TypeScript type definitions for all discovered tools from child servers.

Input:

include_examples (optional boolean) - Whether to include usage examples

Example:

// Call the tool (in your MCP client)
get_tool_definitions({ include_examples: true })

Output: Returns TypeScript code with interfaces and function declarations:

/**
 * Auto-generated TypeScript definitions for MCP tools
 */

interface ToolResult {
  content: Array<{
    type: string;
    text?: string;
    // ...
  }>;
  isError?: boolean;
}

/**
 * Read contents of a file
 * Server: filesystem
 * Tool: read_file
 */
interface ReadFileParams {
  path: string;
}

declare function filesystem_read_file(params: ReadFileParams): Promise<ToolResult>;

// ... more tool definitions

Tool 2: generate_and_execute_code

This tool executes TypeScript code in a sandbox with access to all discovered tool functions.

Input:

code (required string) - TypeScript/JavaScript code to execute
timeout (optional number) - Max execution time in milliseconds (default: 30000, max: 300000)

Example:

// Call the tool with TypeScript code
generate_and_execute_code({
  code: `
    // Read multiple files and combine them
    const file1 = await filesystem_read_file({ path: "/tmp/file1.txt" });
    const file2 = await filesystem_read_file({ path: "/tmp/file2.txt" });

    const text1 = file1.content[0].text;
    const text2 = file2.content[0].text;

    console.log("File 1 length:", text1.length);
    console.log("File 2 length:", text2.length);

    return {
      combined: text1 + text2,
      totalLength: text1.length + text2.length
    };
  `
})

Output:

=== Console Output ===
File 1 length: 42
File 2 length: 38

=== Result ===
{
  "combined": "...",
  "totalLength": 80
}

Sandbox Environment

The TypeScript execution sandbox provides:

Available:

All discovered tool functions (as async functions)
Console methods: console.log(), console.error(), console.warn(), console.info()
Basic JavaScript globals: Math, JSON, Date, Array, Object, String, Number, Boolean
Promise and async/await support
Error handling with try/catch
Timers: setTimeout, setInterval, clearTimeout, clearInterval

Not Available:

Node.js modules (fs, http, child_process, etc.)
File system access (except via MCP tools)
Network access (except via MCP tools)
Process information

Security Note: This is not a fully secure sandbox. The VM context provides isolation but is not bulletproof. Only execute trusted code.

Error Handling

Errors in the sandbox are caught and returned with stack traces:

generate_and_execute_code({
  code: `
    try {
      const result = await filesystem_read_file({ path: "/nonexistent" });
      return result;
    } catch (error) {
      console.error("Failed to read file:", error.message);
      throw error; // Re-throw to surface to parent
    }
  `
})

Testing with Claude Code

Want to try mcpcodeserver with Claude Code? Use the one-command setup:

./setup-claude-code-test.sh

This will build the project, install test dependencies, and show you exactly what to add to your Claude Code configuration. See TESTING_WITH_CLAUDE.md for detailed instructions.

Development

# Install dependencies
bun install

# Build the project
bun run build

# Watch mode for development
bun run dev

# Run the server
bun start

# Run tests
bun test                # All tests
bun run test:unit       # Unit tests only
bun run test:integration # Integration tests (requires Python)

# Code quality
bun run lint            # Check linting
bun run format          # Format code
bun run typecheck       # Type checking

Project Structure

See AGENTS.md for detailed project structure and component documentation.

Use Cases

Multi-File Operations

Instead of making multiple tool calls through the LLM, write code:

const files = ["/tmp/a.txt", "/tmp/b.txt", "/tmp/c.txt"];
const contents = await Promise.all(
  files.map(path => filesystem_read_file({ path }))
);
return contents.map(r => r.content[0].text);

Data Transformation

Process data between tool calls without LLM intervention:

const data = await api_fetch({ url: "https://api.example.com/data" });
const json = JSON.parse(data.content[0].text);
const filtered = json.items.filter(item => item.active);
return filtered.length;

Conditional Logic

Make decisions based on tool results:

const exists = await filesystem_read_file({ path: "/tmp/config.json" });
if (exists.isError) {
  console.log("Config doesn't exist, using defaults");
  return { source: "defaults" };
} else {
  return { source: "file", config: JSON.parse(exists.content[0].text) };
}

Error Recovery

Handle errors gracefully without aborting the entire workflow:

const results = [];
for (const path of ["/tmp/a.txt", "/tmp/b.txt", "/tmp/c.txt"]) {
  try {
    const content = await filesystem_read_file({ path });
    results.push({ path, success: true, data: content });
  } catch (error) {
    results.push({ path, success: false, error: error.message });
  }
}
return results;

Upstream MCP Servers Integration

mcpcodeserver can integrate with official upstream MCP servers from the Model Context Protocol servers repository. This allows you to use real, production-ready MCP servers alongside your custom tools.

Supported Upstream Servers

filesystem: File system operations (read, write, list directories)
memory: In-memory key-value storage
sqlite: SQLite database operations
github: GitHub API integration
brave-search: Web search capabilities
fetch: HTTP request capabilities

Example Configuration

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
    },
    "memory": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-memory"]
    },
    "sqlite": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-sqlite", "--db-path", "/tmp/test.db"]
    }
  }
}

Testing Upstream Integration

The project includes comprehensive tests for upstream server integration:

# Run upstream servers integration tests
bun tests/integration/run-upstream-tests.ts

# Or manually test with upstream config
npx mcpcodeserver --config tests/integration/upstream-test-config.json

Cross-Server Workflows

With upstream servers, you can create powerful cross-server workflows:

// Store database query results in memory and write to file
const queryResult = await sqlite_execute_sql({
  sql: "SELECT COUNT(*) as count FROM users"
});
const count = queryResult.content[0].text;

await memory_create({
  key: "user-count",
  value: count
});

await filesystem_write_file({
  path: "/tmp/user-count.txt",
  content: `Total users: ${count}`
});

Limitations

Execution timeout: Maximum 5 minutes (configurable, default 30 seconds)
Memory: Limited by Node.js VM context
No persistent state between executions
Cannot require/import external modules
Not a security sandbox - don't run untrusted code

Contributing

Contributions welcome! This project is built with:

TypeScript 5.7+
Node.js 18+
MCP TypeScript SDK 1.20+
Zod for validation

See CONTRIBUTING.md for detailed contribution guidelines.

Support

If you find this project helpful, consider buying me a coffee!

License

MIT