lazy-mcp 2.3.1

A proxy tool that converts normal MCP servers to use lazy-loading pattern with meta-tools

Lazy MCP Proxy

A client-agnostic proxy that converts normal MCP servers to use a lazy-loading pattern, dramatically reducing initial context usage by 90%+ and enabling support for hundreds of commands. It works with any MCP client — Claude Desktop, OpenCode, Cursor, VS Code, and more.

Table of Contents

• Table of Contents
• Features
• How It Works
• Installation
• Usage
  • Streamable HTTP Transport
• Integration (Claude Desktop, OpenCode, Cursor, VS Code, and more)
• Example
• Development
  • Running from Local Source
• Releases
  • How It Works
  • Required CI/CD Variables
    • GITLAB_RELEASE_TOKEN
    • NPM_TOKEN
    • PYPI_TOKEN
    • CARGO_TOKEN
• Configuration Reference
  • Server Configuration Fields
  • OAuth 2.0 Authentication
  • Command Format
  • Environment Variables
  • Transport Configuration
  • Logging Configuration
  • Health Monitoring
  • Config Reload (SIGHUP)
• Benefits
• Documentation

Features

• Client-Agnostic: Works with any MCP client — Claude Desktop, OpenCode, Cursor, VS Code, and any other MCP-compatible tool. Unlike client-specific solutions, lazy-mcp works everywhere you do.
• Multi-Server Aggregation: Aggregate multiple MCP servers with on-demand discovery
• Lazy Loading: Only discover tools when needed, not upfront
• Batch Discovery: Discover multiple servers in one call
• 90%+ Context Reduction: From ~16K to ~1.5K tokens initially
• Built-in OAuth 2.0 + PKCE: Authenticate with OAuth-protected remote servers without a browser — works in sandboxed agent environments
• Background Health Monitoring: Probes all servers on startup and periodically; list_servers shows accurate health from the first call
• Hot Config Reload: Send SIGHUP to reload config without restarting — add, remove, or update servers on the fly
• Streamable HTTP Transport: Run as an HTTP server — expose lazy-mcp over the network so remote clients can connect via POST /mcp

How It Works

Aggregates multiple MCP servers and exposes four meta-tools:

• list_servers - Lists all configured MCP servers with health status. Response includes pid and config_file so an agent can fix broken config and reload via kill -HUP <pid>
• list_commands - Discovers tools from specific server(s), supports batch discovery
• describe_commands - Gets detailed schemas from a server
• invoke_command - Executes commands from a specific server

Installation

Homebrew (macOS and Linux, no runtime dependencies):

brew tap gitlab-org/lazy-mcp https://gitlab.com/gitlab-org/ai/lazy-mcp
brew install lazy-mcp

Cargo (if you have Rust installed, no Node.js required):

cargo install lazy-mcp

If you have Python / uv (no Node.js required):

uvx lazy-mcp

If you have Node.js — use npx to always get the latest version:

npx lazy-mcp@latest

Or install globally (locks to specific version):

npm install -g lazy-mcp

Docker / Podman:

docker build -t lazy-mcp .
docker compose up

The image compiles the TypeScript CLI during docker build, so this works from a clean checkout without a prebuilt dist/ directory.

Or with Podman:

podman build -t lazy-mcp .
podman compose up

This runs lazy-mcp in HTTP mode on port 8080 with config mounted from ~/.config/lazy-mcp/servers.json. See docker-compose.yml for configuration options.

Usage

Create a configuration file at ~/.config/lazy-mcp/servers.json:

{
  "servers": [
    {
      "name": "chrome-devtools",
      "description": "Chrome DevTools automation",
      "command": ["npx", "-y", "chrome-devtools-mcp@latest"]
    },
    {
      "name": "gitlab",
      "description": "GitLab MCP server",
      "url": "https://gitlab.com/api/v4/mcp"
    },
    {
      "name": "my-remote-server",
      "description": "Custom remote MCP server with static token",
      "url": "https://api.example.com/mcp",
      "headers": {
        "Authorization": "Bearer ${API_TOKEN}"
      }
    },
    {
      "name": "glean",
      "description": "Glean enterprise search (OAuth)",
      "url": "https://your-company.glean.com/mcp/default"
    }
  ]
}

Then run:

# Using npx (recommended - always latest version)
npx lazy-mcp@latest --config ~/.config/lazy-mcp/servers.json

# Or via environment variable
LAZY_MCP_CONFIG=~/.config/lazy-mcp/servers.json npx lazy-mcp@latest

# Or if installed globally
lazy-mcp --config ~/.config/lazy-mcp/servers.json

Streamable HTTP Transport

By default, lazy-mcp communicates over stdio (standard MCP transport). You can also run it as an HTTP server using the Streamable HTTP transport, allowing remote clients to connect over the network:

Via config file — add a transport block to servers.json:

{
  "servers": [
    { "name": "my-server", "description": "My MCP server", "command": ["python", "server.py"] }
  ],
  "transport": {
    "type": "http",
    "port": 3000,
    "host": "localhost",
    "path": "/mcp",
    "authToken": "${MY_API_KEY}"
  }
}

Via CLI flags (override config values):

# Start HTTP server on port 3000
lazy-mcp --config servers.json --transport http --port 3000

# With custom host, path, and auth
lazy-mcp --config servers.json --transport http --port 3000 --host 127.0.0.1 --path /mcp --auth-token "my-secret"

Security note: --host 0.0.0.0 exposes the HTTP server on all network interfaces. Use it only inside Docker or trusted networks.

Reverse proxy note: The default Origin check uses the scheme visible to lazy-mcp's own socket plus the incoming Host header. If you run lazy-mcp behind a TLS-terminating reverse proxy, the backend hop is usually plain HTTP, so the implicit same-origin shortcut may reject public HTTPS origins. In that setup, configure transport.allowedOrigins explicitly. If your proxy preserves the public Host header, configure transport.allowedHosts too.

Example:

{
  "transport": {
    "type": "http",
    "host": "127.0.0.1",
    "port": 8080,
    "path": "/mcp",
    "allowedHosts": ["mcp.example.com"],
    "allowedOrigins": ["https://mcp.example.com"]
  }
}

lazy-mcp intentionally does not trust Forwarded / X-Forwarded-* headers by default. If proxy-aware origin reconstruction is ever added, it should be behind an explicit trusted-proxy setting.

Via environment variables (lowest precedence):

LAZY_MCP_TRANSPORT=http LAZY_MCP_PORT=3000 LAZY_MCP_AUTH_TOKEN=my-secret lazy-mcp

Precedence: CLI flags > config file > environment variables > defaults.

Once running, clients connect as a remote MCP server:

# Quick test with curl
curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Authorization: Bearer ${MY_API_KEY}" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

Note: Server-initiated notifications via GET/SSE are not supported in stateless mode. Use POST for all requests.

Integration (Claude Desktop, OpenCode, Cursor, VS Code, and more)

Replace multiple MCP server entries with one aggregated proxy:

Before (5 separate MCP servers):

{
  "mcp": {
    "chrome-devtools": { "command": ["npx", "lazy-mcp@latest", "npx", "-y", "chrome-devtools-mcp@latest"] },
    "gitlab": { "command": ["npx", "lazy-mcp@latest", "npx", "mcp-remote@latest", "https://..."] },
    "grepai": { "command": ["npx", "lazy-mcp@latest", "grepai", "mcp-serve"] },
    "context7": { "command": ["npx", "-y", "@upstash/context7-mcp"] },
    "perplexity": { "command": ["npx", "-y", "@perplexity-ai/mcp-server"] }
  }
}

After (Consolidated into 1 multi-server proxy):

{
  "mcp": {
    "lazy-mcp": {
      "type": "local",
      "command": ["npx", "lazy-mcp@latest", "--config", "~/.config/lazy-mcp/servers.json"],
      "enabled": true
    }
  }
}

HTTP mode — for clients that support remote MCP servers:

Start lazy-mcp in HTTP mode (e.g. lazy-mcp --config servers.json --transport http --port 3000), then configure your client:

{
  "mcp": {
    "lazy-mcp": {
      "type": "remote",
      "url": "http://localhost:3000/mcp",
      "headers": {
        "Authorization": "Bearer ${LAZY_MCP_AUTH_TOKEN}"
      }
    }
  }
}

Where ~/.config/lazy-mcp/servers.json contains all 5 servers:

{
  "servers": [
    { "name": "chrome-devtools", "description": "Chrome DevTools automation", "command": ["npx", "-y", "chrome-devtools-mcp@latest"] },
    { "name": "gitlab", "description": "GitLab API integration", "command": ["npx", "mcp-remote@latest", "https://..."] },
    { "name": "grepai", "description": "Search codebase", "command": ["grepai", "mcp-serve"] },
    { "name": "context7", "description": "Library documentation", "command": ["npx", "-y", "@upstash/context7-mcp"] },
    { "name": "perplexity", "description": "Web search", "command": ["npx", "-y", "@perplexity-ai/mcp-server"] }
  ]
}

Result: ~90% context reduction (from ~16K to ~1.5K tokens initially)

Example

# Configure multiple MCP servers in servers.json, then:
npx lazy-mcp@latest --config ~/.config/lazy-mcp/servers.json
# Exposes: list_servers, list_commands, describe_commands, invoke_command (4 meta-tools)
# Instead of loading all tools from all servers upfront (~16K+ tokens),
# the agent discovers tools on-demand (~1.5K tokens initially)

Development

npm install
npm run build
npm test

Running from Local Source

Instead of npx lazy-mcp@latest (which downloads the published package), you can run directly from the cloned repo:

Without building — using ts-node (picks up source changes immediately):

npm run dev -- --config ~/.config/lazy-mcp/servers.json

After building — run the compiled output:

npm run build
node dist/cli.js --config ~/.config/lazy-mcp/servers.json
# or equivalently:
npm start -- --config ~/.config/lazy-mcp/servers.json

In an MCP client config — point directly at the local build:

{
  "mcp": {
    "lazy-mcp": {
      "command": "node",
      "args": ["/path/to/lazy-mcp/dist/cli.js", "--config", "~/.config/lazy-mcp/servers.json"]
    }
  }
}

Or with ts-node (no build needed, always reflects latest source):

{
  "mcp": {
    "lazy-mcp": {
      "command": "npx",
      "args": ["ts-node", "/path/to/lazy-mcp/src/cli.ts", "--config", "~/.config/lazy-mcp/servers.json"]
    }
  }
}

Releases

Releases are fully automated via semantic-release on every push to main.

How It Works

1. CI analyzes all commits since the last tag using Conventional Commits
2. Determines the next version (feat → minor bump, fix/perf/chore/refactor/test → patch bump)
3. Updates package.json, CHANGELOG.md, VERSION, and RELEASE_NOTES.md
4. Commits those files as chore(release): X.Y.Z and pushes a vX.Y.Z tag
5. Creates a GitLab Release with the generated release notes
6. The vX.Y.Z tag triggers a separate pipeline that publishes the package to npm automatically

No manual version bumping or tagging needed — just merge to main with conventional commit messages.

Required CI/CD Variables

Four CI/CD variables must be configured (GitLab → Project → Settings → CI/CD → Variables):

Variable	Description
GITLAB_RELEASE_TOKEN	Project access token — pushes the release commit + tag to main and creates the GitLab Release
NPM_TOKEN	npm automation token — publishes the package to the npm registry on tag pipelines
PYPI_TOKEN	PyPI API token — publishes the package to PyPI on tag pipelines
CARGO_TOKEN	crates.io API token — publishes the crate to crates.io on tag pipelines

GITLAB_RELEASE_TOKEN

Creating the token (GitLab → Project → Settings → Access Tokens):

Setting	Value
Token name	semantic-release-bot (or any name)
Role	Developer (push to a protected branch should be configured separately)
Scopes	api, write_repository

Adding the variable:

Setting	Value
Key	GITLAB_RELEASE_TOKEN
Masked	✅ Yes
Protected	❌ No (must be available on the unprotected main pipeline)

Note: If main is a protected branch with push restrictions, the token's bot user must be added to the "Allowed to push" list under GitLab → Project → Settings → Repository → Protected branches.

NPM_TOKEN

Creating the token (npmjs.com → Account → Access Tokens → Generate New Token):

Setting	Value
Token type	Automation (bypasses 2FA, suitable for CI)

Adding the variable:

Setting	Value
Key	NPM_TOKEN
Masked	✅ Yes
Protected	✅ Yes (only needed on tag pipelines, which are protected)

PYPI_TOKEN

Creating the token (pypi.org → Account Settings → API tokens → Add API token):

Setting	Value
Token name	lazy-mcp-ci (or any name)
Scope	Project: lazy-mcp (restrict to this project after first publish; use "Entire account" for the very first publish)

Adding the variable:

Setting	Value
Key	PYPI_TOKEN
Masked	✅ Yes
Protected	✅ Yes (only needed on tag pipelines, which are protected)

CARGO_TOKEN

Creating the token (crates.io → Account Settings → API Tokens → New Token):

Setting	Value
Token name	lazy-mcp-ci (or any name)
Scopes	publish-new, publish-update

Adding the variable:

Setting	Value
Key	CARGO_TOKEN
Masked	✅ Yes
Protected	✅ Yes (only needed on tag pipelines, which are protected)

Configuration Reference

Server Configuration Fields

Field	Type	Required	Description
name	string	✅	Unique server identifier
description	string	✅	Human-readable description
type	"local" | "remote"	Optional	Inferred from url (remote) or command (local) if omitted
command	string[] | string	For local	Command to execute (array format recommended)
args	string[]	Optional	Arguments (only if command is string)
url	string	For remote	HTTP/HTTPS URL
headers	object	Optional	Static HTTP headers for remote servers
oauth	object	Optional	OAuth 2.0 config for remote servers (see below)
env	object	Optional	Environment variables (supports ${VAR} expansion)
enabled	boolean	Optional	Enable/disable server (default: true)
examples	object[]	Optional	Usage examples shown in list_servers output
tags	string[]	Optional	Capability tags for filtering (e.g. "api", "browser")

OAuth 2.0 Authentication

lazy-mcp has built-in OAuth 2.0 + PKCE support for remote servers that require user authorization. It works without opening a browser automatically, making it suitable for sandboxed agent environments: when authentication is needed, lazy-mcp returns the authorization URL in the error message so the agent can present it to the user.

OAuth server endpoints are discovered automatically via RFC 8414 (/.well-known/oauth-authorization-server). Dynamic client registration (RFC 7591) is used when no clientId is provided.

Tokens are persisted to ~/.config/lazy-mcp/tokens.json (mode 0600) and refreshed automatically via refresh_token when available.

Minimal config (fully automatic — discovery + dynamic registration):

{
  "name": "glean",
  "description": "Glean enterprise search",
  "url": "https://your-company.glean.com/mcp/default",
  "oauth": {}
}

With a pre-registered client ID:

{
  "name": "glean",
  "description": "Glean enterprise search",
  "url": "https://your-company.glean.com/mcp/default",
  "oauth": {
    "clientId": "${GLEAN_CLIENT_ID}",
    "extraHeaders": { "X-Glean-Auth-Type": "OAUTH" }
  }
}

oauth object fields:

Field	Type	Default	Description
clientId	string	—	OAuth client ID. If omitted, dynamic registration (RFC 7591) is attempted
clientSecret	string	—	Client secret (omit for public-client / PKCE-only flows)
callbackPort	number	8947	Local port for the OAuth redirect callback server
extraHeaders	object	—	Additional headers added to every authenticated request (e.g. X-Glean-Auth-Type)

How it works:

1. Agent calls invoke_command (or list_commands) on an OAuth-protected server
2. lazy-mcp returns an isError: true response with the authorization URL
3. Agent presents the URL to the user: "Open this URL to authorize Glean: https://..."
4. User opens the URL in a browser and completes authorization
5. Browser redirects to http://localhost:8947/callback — lazy-mcp captures the token
6. Agent retries the original command — now succeeds transparently

Command Format

Recommended (OpenCode-compatible):

{
  "command": ["npx", "-y", "my-mcp-server", "--port", "3000"]
}

Legacy (still supported):

{
  "command": "npx",
  "args": ["-y", "my-mcp-server", "--port", "3000"]
}

Environment Variables

Use ${VAR_NAME} to reference environment variables:

{
  "env": {
    "API_KEY": "${MY_API_KEY}",
    "DEBUG": "true"
  },
  "headers": {
    "Authorization": "Bearer ${AUTH_TOKEN}"
  }
}

Transport Configuration

Configure how lazy-mcp exposes its MCP endpoint. By default, it uses stdio (for subprocess-based clients). Set type: "http" to run as an HTTP server.

Top-level configuration (in servers.json):

Field	Type	Default	Description
transport.type	"stdio" | "http"	"stdio"	Transport mode
transport.port	number	8080	HTTP server port
transport.host	string	"127.0.0.1"	HTTP server bind address. For TLS-terminating reverse proxies, keep localhost binding and configure allowedOrigins explicitly.
transport.path	string	"/mcp"	MCP endpoint URL path
transport.authToken	string	—	Bearer token for HTTP auth (supports ${VAR} expansion)
transport.allowedOrigins	string[]	—	List of allowed Origin header values for request-origin validation / CSRF protection (e.g. ["https://example.com"]). Full origins including scheme and port. Recommended for TLS-terminating reverse-proxy deployments. Does not send CORS response headers.
transport.allowedHosts	string[]	—	List of explicitly allowed host domains for DNS rebinding protection. If a reverse proxy preserves the public Host header, add that host here.
transport.maxPayloadSize	number	4194304	Maximum request body size in bytes. Requests exceeding this limit return HTTP 413

CLI flags (override config values):

Flag	Env Variable	Description
--transport	LAZY_MCP_TRANSPORT	Transport type (stdio or http)
--port	LAZY_MCP_PORT	HTTP server port
--host	LAZY_MCP_HOST	HTTP server bind address
--path	LAZY_MCP_PATH	MCP endpoint URL path
--auth-token	LAZY_MCP_AUTH_TOKEN	Bearer token for HTTP auth
--request-timeout	LAZY_MCP_REQUEST_TIMEOUT	Request timeout in ms for server calls, including MCP handshake requests and remote response parsing (default: 10000)
--max-payload-size	LAZY_MCP_MAX_PAYLOAD_SIZE	Maximum request body size in bytes (default: 4194304)

When authToken is set, all HTTP requests must include Authorization: Bearer <token> — unauthenticated requests receive 401 Unauthorized.

Logging Configuration

lazy-mcp now emits structured logs to stderr (stdout remains reserved for MCP protocol traffic).

Top-level configuration (in servers.json):

Field	Type	Default	Description
logging.level	"error" | "info" | "debug"	"info"	Minimum log level
logging.format	"json" | "plain"	"json"	Log output format
logging.dumpBodies	boolean	false	Enable debug request/response body dumps
logging.maxBodyLogBytes	number	8192	Max body-dump size in bytes before truncation
logging.redactKeys	string[]	—	Additional case-insensitive keys to redact (merged with built-in defaults)

Built-in redaction includes common secret keys like authorization, token, access_token, refresh_token, client_secret, and headers.authorization.

Example:

{
  "servers": [
    {
      "name": "my-server",
      "description": "Example",
      "command": ["npx", "-y", "my-mcp-server"]
    }
  ],
  "logging": {
    "level": "debug",
    "format": "json",
    "dumpBodies": true,
    "maxBodyLogBytes": 4096,
    "redactKeys": ["my_custom_secret"]
  }
}

Typical access log event fields include:

• client source (clientIp, optional forwardedFor)
• request shape (httpMethod, path, mcpMethod, lazyTool)
• downstream routing (downstreamServer, downstreamCommand)
• outcome (status, reason, durationMs)

Health Monitoring

lazy-mcp includes a background health monitor that probes all servers periodically. The monitor is activity-driven: it sleeps on startup and only begins probing after the first user tool call (list_servers, list_commands, etc.). After a configurable idle timeout (default: 5 minutes) with no tool calls, the monitor goes back to sleep. This prevents OAuth-protected servers (e.g. GitLab via mcp-remote) from opening browser windows when no one is using the tools.

Successful probes populate the discovery cache, so subsequent list_commands calls return instantly from cache.

Top-level configuration (in servers.json):

Field	Type	Default	Description
healthMonitor.enabled	boolean	true	Enable/disable background health monitoring
healthMonitor.interval	number	30000	Interval between health checks (ms)
healthMonitor.timeout	number	10000	Timeout per server probe (ms)
healthMonitor.idleTimeout	number	300000	Stop probing after this much inactivity (ms). 0 = never sleep (legacy)
requestTimeout	number	10000	Timeout for individual server requests. For remote HTTP servers, this includes waiting for headers, reading response bodies, and SSE response parsing. Override via --request-timeout or LAZY_MCP_REQUEST_TIMEOUT

To disable health monitoring:

{
  "servers": [...],
  "healthMonitor": { "enabled": false }
}

To increase the request timeout (e.g. for slow remote servers):

{
  "servers": [...],
  "requestTimeout": 30000
}

Config Reload (SIGHUP)

You can reload the configuration without restarting the process by sending a SIGHUP signal:

kill -HUP $(pgrep -f lazy-mcp)

This will:

• Re-read and validate the config file
• Add newly configured servers (lazy connection on first use)
• Remove servers no longer in config (closes connections)
• Reconnect servers whose config changed (updated URL, env, etc.)
• Preserve unchanged servers (keeps existing connections and caches)
• Restart the health monitor and probe all servers

If the new config is invalid, the reload is rejected and the current config continues running. All reload activity is logged to stderr.

Note: SIGHUP is not available on Windows.

Benefits

• 90%+ context reduction - From ~16K to ~1.5K tokens initially
• Progressive tool discovery - Only load schemas when needed
• Multi-server aggregation - Manage multiple MCP servers in one config
• Batch discovery - Discover multiple servers efficiently
• Scales to hundreds of commands without context bloat
• Flexible configuration - Enable/disable servers on demand
• Environment variable support - Secure credential management
• Both local and remote - Support for subprocess and HTTP servers
• Streamable HTTP transport - Run as an HTTP server for remote client access
• Health monitoring - Background probes detect broken servers before you hit them

Documentation

• CHANGELOG.md - Version history and release notes
• AGENTS.md - Development guide for AI coding agents (build commands, code style, testing patterns)
• doc/ARCHITECTURE.md - Architecture overview and design patterns
• doc/CONTRIBUTING.md - Contributing guide with common development tasks
• doc/requests/ - Bruno API collection for testing the Streamable HTTP transport. Open the doc/requests/ folder as a collection in Bruno, select the local or local-with-auth environment, and run requests against a locally running lazy-mcp --transport http instance.
• Configuration Reference - Server configuration options (above)