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FrontMCP servers are composed of one or more apps. Each @App is an isolated container with its own tools, resources, prompts, providers, and authentication — composed together under a single @FrontMcp server.

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Composing Apps

@FrontMcp({
  info: { name: 'Platform Server', version: '1.0.0' },
  apps: [CrmApp, AnalyticsApp, AdminApp],
})
export default class Server {}
Each app defines its own capabilities: 
@App({
  id: 'crm',
  name: 'CRM',
  tools: [CreateLeadTool, GetContactsTool],
  resources: [LeadResource],
  providers: [CrmDatabaseProvider],
})
class CrmApp {}

@App({
  id: 'analytics',
  name: 'Analytics',
  tools: [RunReportTool, ExportDataTool],
  providers: [AnalyticsDatabaseProvider],
})
class AnalyticsApp {}

@App({
  id: 'admin',
  name: 'Admin',
  tools: [ManageUsersTool],
})
class AdminApp {}

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What Each App Gets

FeatureScope
Tools, Resources, PromptsRegistered under the app’s namespace
ProvidersIsolated to the app (server-level providers are shared)
AuthenticationPer-app auth configuration
SkillsRegistered and searchable within the app
PluginsCan be app-specific or server-wide

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Shared vs Isolated Providers

// Server-level: shared across all apps
@FrontMcp({
  providers: [SharedCacheProvider, LoggingProvider],
  apps: [CrmApp, AnalyticsApp],
})
class Server {}

// App-level: isolated to CRM only
@App({
  id: 'crm',
  providers: [CrmDatabaseProvider],
  tools: [CreateLeadTool],
})
class CrmApp {}
Tools in CrmApp can access both SharedCacheProvider and CrmDatabaseProvider, while tools in AnalyticsApp can only access SharedCacheProvider.

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ESM Package Apps

You can also compose apps from npm packages or remote MCP servers at runtime via App.esm() and App.remote(): 
import { FrontMcp, App } from '@frontmcp/sdk';

@FrontMcp({
  info: { name: 'Platform', version: '1.0.0' },
  apps: [
    CrmApp,                                         // Local app
    App.esm('@acme/analytics@^2.0.0'),              // ESM package
    App.remote('https://ext.example.com/mcp'),      // Remote app
  ],
})
export default class Server {}
ESM packages get their own tool, resource, and prompt registries with full hook and lifecycle support, but do not support plugins or adapters (use local @App classes for those).

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Learn More

Apps

Full guide to @App configuration and capabilities

Server

Server-level composition and configuration

ESM Packages

Load npm packages at runtime as MCP apps