LuaMCPServer

Overview

LuaMCPServer allows you to connect external MCP (Model Context Protocol) servers to your agent. MCP servers provide additional tools that your agent can use at runtime, enabling integration with APIs, databases, documentation services, and more.

import { LuaMCPServer, env } from 'lua-cli';

const docsServer = new LuaMCPServer({
  name: 'docs',
  transport: 'streamable-http',
  url: 'https://mcp.example.com/mcp',
  headers: () => ({
    'Authorization': `Bearer ${env("MCP_API_KEY")}`
  })
});

export default docsServer;

What is MCP? The Model Context Protocol (MCP) is an open standard for connecting AI models to external tools and data sources. Learn more at modelcontextprotocol.io.

Why MCP Servers?

Extend Capabilities

Add tools without writing code - use existing MCP servers

Standard Protocol

Compatible with any MCP-compliant server

Remote Integration

Connect to hosted MCP services via HTTP

Community Ecosystem

Access growing library of hosted MCP servers

Transport Types

MCP servers support two HTTP-based transport methods:

Streamable HTTP (Recommended)
SSE (Legacy)

Best for: Modern MCP servers, most use casesThe modern MCP standard (spec 2025-03-26) with bidirectional communication.

const server = new LuaMCPServer({
  name: 'my-server',
  transport: 'streamable-http',
  url: 'https://mcp.example.com/mcp',
  headers: () => ({
    'Authorization': `Bearer ${env("API_KEY")}`
  })
});

Best for: Older MCP servers that don’t support Streamable HTTPUses Server-Sent Events for server-to-client streaming.

const server = new LuaMCPServer({
  name: 'legacy-server',
  transport: 'sse',
  url: 'https://old-mcp.example.com/sse',
  headers: () => ({
    'Authorization': `Bearer ${env("API_KEY")}`
  })
});

stdio transport not supported yet: Local MCP servers (using npx, node, etc.) are not supported yet. Please use remote MCP servers with streamable-http or sse transport instead.

Constructor

new LuaMCPServer(config)

Creates a new MCP server configuration.

config

LuaMCPServerConfig

required

MCP server configuration object

Configuration Parameters

Required Fields

name

string

required

Unique identifier for the MCP serverFormat: lowercase, hyphens allowedExamples: 'docs-server', 'api-gateway', 'database'

transport

'streamable-http' | 'sse'

required

Transport protocol for communication

'streamable-http' - Modern MCP standard (recommended)
'sse' - Legacy Server-Sent Events transport

url

string | (() => string)

required

URL of the remote MCP serverCan be a static string or a function that returns the URL at runtime using env().Examples:

'https://mcp.example.com/mcp'
() => env("MCP_SERVER_URL")

Optional Fields

headers

Record<string, string> | (() => Record<string, string>)

HTTP headers to send with requestsCan be a static object or a function that returns headers at runtime using env().Example (static): { 'X-Custom-Header': 'value' }Example (dynamic): () => ({ 'Authorization': \Bearer $` })`

timeout

number

Timeout in milliseconds for server operationsDefault: 60000 (60 seconds)

Examples

Documentation Server

import { LuaMCPServer, env } from 'lua-cli';

const docsServer = new LuaMCPServer({
  name: 'docs',
  transport: 'streamable-http',
  url: 'https://docs.example.com/mcp',
  headers: () => ({
    'Authorization': `Bearer ${env("DOCS_API_KEY")}`
  }),
  timeout: 30000
});

export default docsServer;

API Gateway

import { LuaMCPServer, env } from 'lua-cli';

const apiServer = new LuaMCPServer({
  name: 'api-gateway',
  transport: 'streamable-http',
  url: 'https://api.example.com/mcp',
  headers: () => ({
    'Authorization': `Bearer ${env("API_TOKEN")}`,
    'X-Api-Version': '2024-01'
  }),
  timeout: 45000
});

export default apiServer;

Database Service

import { LuaMCPServer, env } from 'lua-cli';

const dbServer = new LuaMCPServer({
  name: 'database',
  transport: 'streamable-http',
  url: 'https://db-mcp.example.com/mcp',
  headers: () => ({
    'Authorization': `Bearer ${env("DB_API_KEY")}`,
    'X-Database': 'production'
  }),
  timeout: 60000
});

export default dbServer;

Dynamic URL with env()

import { LuaMCPServer, env } from 'lua-cli';

const server = new LuaMCPServer({
  name: 'dynamic-server',
  transport: 'streamable-http',
  url: () => env("MCP_SERVER_URL"),
  headers: () => ({
    'Authorization': `Bearer ${env("API_TOKEN")}`
  })
});

export default server;

Legacy SSE Server

import { LuaMCPServer, env } from 'lua-cli';

const legacyServer = new LuaMCPServer({
  name: 'legacy-api',
  transport: 'sse',
  url: 'https://old-mcp.example.com/sse',
  headers: () => ({
    'Authorization': `Bearer ${env("API_KEY")}`
  })
});

export default legacyServer;

Using with LuaAgent

MCP servers are added to your agent configuration:

import { LuaAgent, LuaSkill, env } from 'lua-cli';

const docsServer = new LuaMCPServer({
  name: 'docs',
  transport: 'streamable-http',
  url: 'https://docs.example.com/mcp',
  headers: () => ({
    'Authorization': `Bearer ${env("DOCS_API_KEY")}`
  })
});

const coreSkill = new LuaSkill({
  name: 'core-skill',
  description: 'Core functionality',
  tools: [...]
});

export const agent = new LuaAgent({
  name: 'docs-assistant',
  persona: 'You are an assistant with access to documentation.',
  skills: [coreSkill],
  
  // Add MCP servers
  mcpServers: [docsServer]
});

Lifecycle Management

Compile

During lua compile, MCP servers are:

Detected from your source code
Registered with the server (if new)
Assigned an ID stored in lua.skill.yaml
Configuration written to dist/mcp-servers.json

Push

Push individual MCP server:

lua push mcp
# Select server from list

Or push all components:

lua push all --force

Activate / Deactivate

MCP servers start inactive. Activate to make tools available:

lua mcp activate
# Select server to activate

lua mcp deactivate
# Select server to deactivate

List / Delete

lua mcp list              # Show all MCP servers
lua mcp delete            # Remove an MCP server

YAML Configuration

After compilation, lua.skill.yaml tracks MCP servers:

agent:
  agentId: your-agent-id
  persona: ...

mcpServers:
  - name: docs
    mcpServerId: mcp_abc123
  - name: api-gateway
    mcpServerId: mcp_def456

The YAML only stores name and mcpServerId. The full configuration (url, headers, etc.) lives in your source code.

Best Practices

Use env() for Secrets

Always use env() for API keys and tokens

// ✅ Good - resolved at runtime
headers: () => ({
  'Authorization': `Bearer ${env("API_KEY")}`
})

// ❌ Bad - hardcoded secret
headers: {
  'Authorization': 'Bearer sk_live_xxxx'
}

Set Appropriate Timeouts

Adjust timeout based on expected operation duration

// Quick operations
timeout: 10000  // 10 seconds

// Database queries
timeout: 30000  // 30 seconds

// Heavy processing
timeout: 120000 // 2 minutes

Use Streamable HTTP for New Integrations

Prefer streamable-http transport for new MCP server integrations

// ✅ Recommended - modern standard
transport: 'streamable-http'

// Use only for legacy servers
transport: 'sse'

Activate Only What You Need

Keep unused servers deactivated to reduce overhead

# Activate only when needed
lua mcp activate docs-server

# Deactivate when done
lua mcp deactivate docs-server

Troubleshooting

Server not found after push

Make sure the server is activated:

lua mcp list      # Check status
lua mcp activate  # Activate if needed

Connection timeout

Check the URL is accessible and increase timeout:

const server = new LuaMCPServer({
  transport: 'streamable-http',
  url: 'https://...',
  timeout: 120000  // Increase timeout
});

Authentication failed

Verify your API key is correct and set in environment:

# Check environment variable is set
lua env production

# Set the variable
lua env production -k API_KEY -v "your-api-key"

stdio transport error

Local MCP servers (stdio) are no longer supported. Migrate to remote servers:

// ❌ No longer supported
transport: 'stdio',
command: 'npx',
args: [...]

// ✅ Use remote transport instead
transport: 'streamable-http',
url: 'https://mcp.example.com/mcp',
headers: () => ({ ... })

LuaAgent

Agent configuration with MCP servers

LuaSkill

Custom tool collections

Environment

Managing environment variables

MCP Command

CLI management commands

Getting Started

Core Concepts

CLI Commands

API Reference

Template & Examples

Overview

Why MCP Servers?

Extend Capabilities

Standard Protocol

Remote Integration

Community Ecosystem

Transport Types

Constructor

new LuaMCPServer(config)

Configuration Parameters

Required Fields

Optional Fields

Examples

Documentation Server

API Gateway

Database Service

Dynamic URL with env()

Legacy SSE Server

Using with LuaAgent

Lifecycle Management

Compile

Push

Activate / Deactivate

List / Delete

YAML Configuration

Best Practices

Troubleshooting

LuaAgent

LuaSkill

Environment

MCP Command

See Also

Getting Started

Core Concepts

CLI Commands

API Reference

Template & Examples

​Overview

​Why MCP Servers?

Extend Capabilities

Standard Protocol

Remote Integration

Community Ecosystem

​Transport Types

​Constructor

​new LuaMCPServer(config)

​Configuration Parameters

​Required Fields

​Optional Fields

​Examples

​Documentation Server

​API Gateway

​Database Service

​Dynamic URL with env()

​Legacy SSE Server

​Using with LuaAgent

​Lifecycle Management

​Compile

​Push

​Activate / Deactivate

​List / Delete

​YAML Configuration

​Best Practices

​Troubleshooting

​Related APIs

LuaAgent

LuaSkill

Environment

MCP Command

​See Also

Overview

Why MCP Servers?

Transport Types

Constructor

new LuaMCPServer(config)

Configuration Parameters

Required Fields

Optional Fields

Examples

Documentation Server

API Gateway

Database Service

Dynamic URL with env()

Legacy SSE Server

Using with LuaAgent

Lifecycle Management

Compile

Push

Activate / Deactivate

List / Delete

YAML Configuration

Best Practices

Troubleshooting

Related APIs

See Also