> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agentfront.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Dependency Injection

> Type-safe dependency injection with @Provider and scoped containers

FrontMCP includes a built-in dependency injection system. Define services with `@Provider`, inject them into tools, resources, prompts, and agents with `this.get()`.

## Defining Providers

Create a provider with a token and scope:

```ts theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
import { Provider } from '@frontmcp/sdk';

export const CONFIG_TOKEN = Symbol('Config');

@Provider({
  token: CONFIG_TOKEN,
  scope: 'singleton',
})
export class ConfigProvider {
  readonly apiKey = process.env.API_KEY!;
  readonly baseUrl = process.env.BASE_URL!;

  static factory() {
    return new ConfigProvider();
  }
}
```

## Provider Scopes

| Scope       | Lifetime                           | Use Case                            |
| ----------- | ---------------------------------- | ----------------------------------- |
| `singleton` | One instance per server            | Configuration, database connections |
| `request`   | One instance per MCP request       | Request-scoped caches, loggers      |
| `context`   | One instance per execution context | Per-tool state                      |

## Injecting Providers

Use `this.get()` or `this.tryGet()` inside any context class:

```ts theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
@Tool({
  name: 'fetch-data',
  inputSchema: { url: z.string() },
})
class FetchDataTool extends ToolContext {
  async execute({ url }: { url: string }) {
    const config = this.get(CONFIG_TOKEN);    // Throws if not found
    const cache = this.tryGet(CACHE_TOKEN);   // Returns undefined if not found

    const response = await this.fetch(url, {
      headers: { Authorization: `Bearer ${config.apiKey}` },
    });

    return response.json();
  }
}
```

## Registering Providers

Register providers at the server or app level:

```ts theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
// Server-level — available to all apps
@FrontMcp({
  info: { name: 'Server', version: '1.0.0' },
  apps: [MyApp],
  providers: [ConfigProvider, DatabaseProvider],
})
class Server {}

// App-level — available only within this app
@App({
  id: 'crm',
  name: 'CRM',
  tools: [CreateLeadTool],
  providers: [CrmServiceProvider],
})
class CrmApp {}
```

<Info>
  Server-level providers are shared across all apps. App-level providers are isolated to their app.
</Info>

## Learn More

<CardGroup cols={2}>
  <Card title="Providers Guide" icon="syringe" href="/frontmcp/extensibility/providers">
    Full guide to defining, scoping, and composing providers
  </Card>

  <Card title="@Provider Reference" icon="code" href="/frontmcp/sdk-reference/decorators/provider">
    Complete decorator API reference
  </Card>
</CardGroup>