Environment Configuration

The ConfigPlugin provides typed environment variable access for your FrontMCP servers. It automatically loads .env and .env.local files, and exposes configuration via this.config in all execution contexts.

Built-in Feature

ConfigPlugin is built into the SDK - no separate installation required. Just import and use:

import { ConfigPlugin } from '@frontmcp/sdk';

Why Use ConfigPlugin?

Typed Access

Type-safe environment variable access with getRequired(), getNumber(), getBoolean()

Auto-Loading

Automatically loads .env and .env.local files with proper precedence

Schema Validation

Optional Zod schema validation for fail-fast configuration errors

DI Integration

Access via this.config in tools, resources, prompts, and other contexts

Quick Start

1. Create your .env files

# .env - Base configuration (committed to git)
DATABASE_URL=postgres://localhost:5432/myapp
API_TIMEOUT=30000
DEBUG=false

# .env.local - Local overrides (gitignored)
DATABASE_URL=postgres://localhost:5432/myapp_dev
DEBUG=true

2. Add ConfigPlugin to your server

import { FrontMcp, App, ConfigPlugin } from '@frontmcp/sdk';

@App({
  name: 'my-app',
  plugins: [
    ConfigPlugin.init({
      basePath: __dirname,      // Directory containing .env files
      loadEnv: true,            // Load .env files (default: true)
      populateProcessEnv: true, // Set process.env values (default: true)
    }),
  ],
  tools: [MyTool],
})
class MyApp {}

@FrontMcp({
  info: { name: 'My Server', version: '1.0.0' },
  apps: [MyApp],
})
export default class Server {}

3. Use this.config in your tools

import { Tool, ToolContext } from '@frontmcp/sdk';
import { z } from 'zod';

@Tool({
  name: 'connect-db',
  description: 'Connect to the database',
  inputSchema: z.object({}),
})
export default class ConnectDbTool extends ToolContext {
  async execute() {
    // Get required config (throws if missing)
    const dbUrl = this.config.getRequired('DATABASE_URL');

    // Get with default value
    const timeout = this.config.getNumber('API_TIMEOUT', 5000);

    // Check existence
    const isDebug = this.config.getBoolean('DEBUG', false);

    return { connected: true, debug: isDebug };
  }
}

Configuration Options

Configure the plugin when initializing:

ConfigPlugin.init({
  basePath: __dirname,        // Base directory for resolving paths
  envPath: '.env',            // Path to base env file (default: '.env')
  localEnvPath: '.env.local', // Path to local override file (default: '.env.local')
  loadEnv: true,              // Whether to load .env files (default: true)
  populateProcessEnv: true,   // Whether to set process.env (default: true)
  schema: envSchema,          // Optional Zod schema for validation
})

basePath

string

Base directory for resolving relative .env paths. Required for file loading.

envPath

string

default:"'.env'"

Path to the base environment file, relative to basePath.

localEnvPath

string

default:"'.env.local'"

Path to the local override file, relative to basePath. Values in this file override the base file.

loadEnv

boolean

default:"true"

Whether to load .env files. Set to false if you only want to read from process.env.

populateProcessEnv

boolean

default:"true"

Whether to set loaded values into process.env. Does not override existing values.

schema

z.ZodType

Optional Zod schema to validate the configuration. Throws ConfigValidationError if validation fails.

ConfigService API

Access configuration values via this.config in any execution context:

get(key, defaultValue?)

Get a configuration value with optional default:

// Returns string | undefined
const apiKey = this.config.get('API_KEY');

// Returns string (uses default if not found)
const region = this.config.get('AWS_REGION', 'us-east-1');

getRequired(key)

Get a required configuration value. Throws ConfigMissingError if not found:

// Throws ConfigMissingError if DATABASE_URL is not set
const dbUrl = this.config.getRequired('DATABASE_URL');

has(key)

Check if a configuration key exists:

if (this.config.has('OPTIONAL_FEATURE')) {
  // Enable optional feature
}

getAll()

Get all configuration values as a record:

const allConfig = this.config.getAll();
console.log(Object.keys(allConfig).length, 'config values loaded');

getNumber(key, defaultValue?)

Parse a configuration value as a number:

// Returns NaN if not found or not a number
const port = this.config.getNumber('PORT');

// Returns 3000 if PORT is not set
const port = this.config.getNumber('PORT', 3000);

getBoolean(key, defaultValue?)

Parse a configuration value as a boolean:

// Returns true for 'true', '1', 'yes', 'on' (case-insensitive)
const debug = this.config.getBoolean('DEBUG', false);

Schema Validation

Define a Zod schema to validate your configuration at startup:

import { z } from 'zod';
import { ConfigPlugin } from '@frontmcp/sdk';

const envSchema = z.object({
  DATABASE_URL: z.string().url(),
  API_KEY: z.string().min(10),
  PORT: z.coerce.number().default(3000),
  DEBUG: z.coerce.boolean().default(false),
});

ConfigPlugin.init({
  basePath: __dirname,
  schema: envSchema,
})

When schema validation is enabled, missing or invalid values will throw ConfigValidationError during server startup, preventing the server from running with invalid configuration.

File Loading Behavior

Precedence Rules

Base file (.env) is loaded first
Local file (.env.local) overrides base values
Existing process.env values are not overwritten

Supported Syntax

# Comments start with #
DATABASE_URL=postgres://localhost:5432/myapp

# Quoted values (single or double quotes)
API_KEY="secret-key-with-spaces"
MESSAGE='Hello, World!'

# Empty values
EMPTY_VAR=

# Escape sequences in double quotes
MULTILINE="line1\nline2\ttabbed"

Add .env.local to your .gitignore file to keep local secrets out of version control.

CLI Integration

The frontmcp dev command automatically loads .env files before starting your server:

# Automatically loads .env and .env.local from current directory
frontmcp dev

# Your server starts with environment variables already set

The CLI loads environment files before spawning your server process, so process.env values are available immediately.

Error Handling

ConfigMissingError

Thrown when getRequired() is called for a missing key:

import { ConfigMissingError } from '@frontmcp/sdk';

try {
  const secret = this.config.getRequired('MISSING_KEY');
} catch (error) {
  if (error instanceof ConfigMissingError) {
    console.error(`Missing config: ${error.key}`);
  }
}

ConfigValidationError

Thrown when schema validation fails:

// At server startup, if DATABASE_URL is invalid:
// ConfigValidationError: Configuration validation failed
//   - DATABASE_URL: Invalid url

Complete Example

import { FrontMcp, App, Tool, ToolContext, ConfigPlugin } from '@frontmcp/sdk';
import { z } from 'zod';

// Define configuration schema
const envSchema = z.object({
  DATABASE_URL: z.string().url(),
  API_KEY: z.string(),
  PORT: z.coerce.number().default(3000),
  DEBUG: z.coerce.boolean().default(false),
  CACHE_TTL: z.coerce.number().default(3600),
});

// Tool that uses configuration
@Tool({
  name: 'get-config-info',
  description: 'Get current configuration status',
  inputSchema: z.object({}),
})
class GetConfigInfoTool extends ToolContext {
  async execute() {
    return {
      debug: this.config.getBoolean('DEBUG'),
      port: this.config.getNumber('PORT'),
      cacheTtl: this.config.getNumber('CACHE_TTL', 3600),
      hasApiKey: this.config.has('API_KEY'),
    };
  }
}

@App({
  name: 'config-demo',
  plugins: [
    ConfigPlugin.init({
      basePath: __dirname,
      schema: envSchema,
    }),
  ],
  tools: [GetConfigInfoTool],
})
class ConfigDemoApp {}

@FrontMcp({
  info: { name: 'Config Demo Server', version: '1.0.0' },
  apps: [ConfigDemoApp],
  http: { port: 3000 },
})
export default class Server {}

Links & Resources

Source Code

View the ConfigPlugin source code

Providers Guide

Learn about dependency injection and providers

Plugins Overview

Learn about the FrontMCP plugin system

Demo Application

See ConfigPlugin in action with real examples

Get Started

Servers

Authentication

Extensibility

Adapters

Plugins

Testing

Guides

Deployment

​Built-in Feature

​Why Use ConfigPlugin?

Typed Access

Auto-Loading

Schema Validation

DI Integration

​Quick Start

​1. Create your .env files

​2. Add ConfigPlugin to your server

​3. Use this.config in your tools

​Configuration Options

​ConfigService API

​get(key, defaultValue?)

​getRequired(key)

​has(key)

​getAll()

​getNumber(key, defaultValue?)

​getBoolean(key, defaultValue?)

​Schema Validation

​File Loading Behavior

​Precedence Rules

​Supported Syntax

​CLI Integration

​Error Handling

​ConfigMissingError

​ConfigValidationError

​Complete Example

​Links & Resources

Source Code

Providers Guide

Plugins Overview

Demo Application

Built-in Feature

Why Use ConfigPlugin?

Quick Start

1. Create your .env files

2. Add ConfigPlugin to your server

3. Use this.config in your tools

Configuration Options

ConfigService API

get(key, defaultValue?)

getRequired(key)

has(key)

getAll()

getNumber(key, defaultValue?)

getBoolean(key, defaultValue?)

Schema Validation

File Loading Behavior

Precedence Rules

Supported Syntax

CLI Integration

Error Handling

ConfigMissingError

ConfigValidationError

Complete Example

Links & Resources