---
title: "Add type safety with TypeScript"
description: "Type safety and TypeScript features in the Nuxt MCP module."
canonical_url: "https://mcp-toolkit.nuxt.dev/advanced/typescript"
---
# Add type safety with TypeScript

> Type safety and TypeScript features in the Nuxt MCP module.

## Type Safety

The Nuxt MCP module provides full TypeScript support with complete type inference and type safety.

## Auto-Imports

All helper functions and types are auto-imported in your server files:

**Functions:**

- `defineMcpTool`, `defineMcpResource`, `defineMcpPrompt`, `defineMcpHandler`, `defineMcpApp`
- `imageResult`, `audioResult` (binary media helpers for tool responses)
- `completable`, `extractToolNames`
- `useMcpSession`, `useMcpServer`, `useMcpLogger`, `useMcpElicitation`, `useMcpApp`
- `listMcpTools`, `listMcpResources`, `listMcpPrompts`, `listMcpDefinitions`
- `getMcpTools`, `getMcpResources`, `getMcpPrompts`

<callout color="warning" icon="i-lucide-triangle-alert">

The `textResult`, `jsonResult`, and `errorResult` helpers are **deprecated**. Return strings, numbers, booleans, objects, or arrays directly from your handler — the toolkit auto-wraps them. For errors, throw an `Error` or use `createError` from `h3`. See [Errors & caching](https://mcp-toolkit.nuxt.dev/tools/errors-caching).

</callout>

**Types:**

- `McpRequestExtra` — extra arguments passed to every tool, prompt, and resource handler (abort signal, auth info, session ID, metadata). Equivalent to `RequestHandlerExtra<ServerRequest, ServerNotification>` from the SDK.
- `McpServerHelper` — return type of [`useMcpServer()`](https://mcp-toolkit.nuxt.dev/advanced/dynamic-definitions#mid-session-registration).
- `McpSessionStore` — typed store returned by [`useMcpSession()`](https://mcp-toolkit.nuxt.dev/advanced/sessions).
- `McpClientNotifier`, `McpLogger`, `McpRequestLogger`, `McpUserFields`, `McpSessionFields` — types behind [`useMcpLogger()`](https://mcp-toolkit.nuxt.dev/advanced/logging).
- `McpElicitation`, `ElicitationFormParams`, `ElicitationFormResult`, `ElicitationUrlParams`, `ElicitationUrlResult`, `ElicitationMode` — types behind [`useMcpElicitation()`](https://mcp-toolkit.nuxt.dev/advanced/elicitation).
- Common SDK protocol types are re-exported from a single import path: `Annotations`, `CallToolResult`, `GetPromptResult`, `ReadResourceResult`, `Resource`, `ServerNotification`, `ServerRequest`, `ToolAnnotations`.

<callout color="warning" icon="i-lucide-triangle-alert">

The aliases `McpToolExtra`, `McpPromptExtra`, and `McpResourceExtra` are kept for back-compat but **deprecated** — they all resolve to `McpRequestExtra`. Prefer the canonical name in new code.

</callout>

```typescript
import { z } from 'zod'

export default defineMcpTool({
  name: 'example',
  inputSchema: {
    message: z.string(),
  },
  handler: async ({ message }, extra: McpRequestExtra) => {
    // message is typed as string
    // extra.signal, extra.authInfo, extra.sessionId are available
  },
})
```

You can disable auto-imports entirely with `autoImports: false` in your [configuration](https://mcp-toolkit.nuxt.dev/getting-started/configuration) and import explicitly from `@nuxtjs/mcp-toolkit/server` instead.

## Type Inference

### Tool Input Types

Input types are automatically inferred from your `inputSchema`:

```typescript
import { z } from 'zod'
import { defineMcpTool } from '@nuxtjs/mcp-toolkit/server'

export default defineMcpTool({
  name: 'example',
  inputSchema: {
    name: z.string(),
    age: z.number(),
    email: z.string().email().optional(),
  },
  handler: async ({ name, age, email }) => {
    // name: string
    // age: number
    // email: string | undefined
  },
})
```

### Tool Output Types

Output types are inferred from `outputSchema`:

```typescript
import { z } from 'zod'
import { defineMcpTool } from '@nuxtjs/mcp-toolkit/server'

export default defineMcpTool({
  name: 'example',
  inputSchema: {
    value: z.number(),
  },
  outputSchema: {
    result: z.number(),
    doubled: z.number(),
  },
  handler: async ({ value }) => {
    const result = value * 2

    return {
      structuredContent: {
        result,      // TypeScript knows this is number
        doubled: result * 2, // TypeScript knows this is number
      },
    }
  },
})
```

### Prompt Argument Types

Prompt argument types are inferred from `inputSchema`:

```typescript
import { defineMcpPrompt } from '@nuxtjs/mcp-toolkit/server'

export default defineMcpPrompt({
  name: 'example',
  inputSchema: {
    text: z.string(),
    maxLength: z.string().optional(),
  },
  handler: async ({ text, maxLength }) => {
    // text: string
    // maxLength: string | undefined
  },
})
```

## Runtime Config Types

Access typed runtime configuration:

```typescript [server/api/config.ts]
export default defineEventHandler((event) => {
  const config = useRuntimeConfig(event).mcp

  // config is typed with:
  // - enabled: boolean
  // - route: string
  // - browserRedirect: string
  // - name: string
  // - version: string
  // - dir: string

  return config
})
```

## Next Steps

- [Tools](https://mcp-toolkit.nuxt.dev/tools/overview) - Learn about creating tools
- [Resources](https://mcp-toolkit.nuxt.dev/resources/overview) - Learn about creating resources
- [Prompts](https://mcp-toolkit.nuxt.dev/prompts/overview) - Learn about creating prompts


## Sitemap

See the full [sitemap](https://mcp-toolkit.nuxt.dev/sitemap.md) for all pages.