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

# Getting started

> First steps with Google middleware for tracking AI costs.

## Installation

<CodeGroup>
  ```bash npm theme={null}
  npm install @ai-billing/google @ai-billing/core @ai-sdk/google ai
  ```

  ```bash pnpm theme={null}
  pnpm add @ai-billing/google @ai-billing/core @ai-sdk/google ai
  ```

  ```bash yarn theme={null}
  yarn add @ai-billing/google @ai-billing/core @ai-sdk/google ai
  ```
</CodeGroup>

## Overview

The `@ai-billing/google` package provides middleware for tracking token usage and calculating costs when using Google models with the Vercel AI SDK.

It captures Google-specific metrics, such as `internalReasoningTokens`, `inputCacheReadTokens`, and `inputCacheWriteTokens`, ensuring that Prompt Caching and reasoning costs are accurately reflected.

## Usage

To use the middleware, wrap your Google model using `wrapLanguageModel` from the `ai` package and pass the `createGoogleMiddleware`.

<Steps>
  <Step title="Initialize the Google provider">
    First, set up the Google provider using your API key.

    ```typescript theme={null}
    import { createGoogleGenerativeAI } from '@ai-sdk/google';

    const google = createGoogleGenerativeAI({
      apiKey: process.env.GOOGLE_AI_STUDIO_KEY,
    });
    ```
  </Step>

  <Step title="Define model pricing">
    Set up a price resolver to define the costs for the models you'll be using. For Google, you can specify costs for standard prompt/completion tokens, cached tokens (`inputCacheReadTokens` and `inputCacheWriteTokens`), and `internalReasoningTokens`.

    ```typescript theme={null}
    import { createObjectPriceResolver } from '@ai-billing/core';

    const priceResolver = createObjectPriceResolver({
      'models/gemini-3.1-flash-lite-preview': {
        promptTokens: 0.00000025, // $0.25 per 1M tokens
        completionTokens: 0.0000015, // $1.50 per 1M tokens
        inputCacheReadTokens: 0.000000025, // $0.025 per 1M tokens
        inputCacheWriteTokens: 0.00000008333333, // ~$0.083 per 1M tokens
        internalReasoningTokens: 0.0000015, // $1.50 per 1M tokens
      },
    });
    ```
  </Step>

  <Step title="Create the billing middleware">
    Initialize the Google billing middleware. You need to provide a destination (such as `consoleDestination`) where billing events will be sent, along with your `priceResolver`.

    ```typescript theme={null}
    import { createGoogleMiddleware } from '@ai-billing/google';
    import { consoleDestination } from '@ai-billing/core';

    const billingMiddleware = createGoogleMiddleware({
      destinations: [consoleDestination()],
      priceResolver: priceResolver,
    });
    ```
  </Step>

  <Step title="Wrap the model">
    Use `wrapLanguageModel` from the `ai` package to apply the billing middleware to your Google model.

    ```typescript theme={null}
    import { wrapLanguageModel } from 'ai';

    const wrappedModel = wrapLanguageModel({
      model: google('models/gemini-3.1-flash-lite-preview'),
      middleware: billingMiddleware,
    });
    ```
  </Step>

  <Step title="Use the wrapped model">
    Finally, use the wrapped model with AI SDK functions like `generateText` or `streamText`. The billing middleware will automatically track tokens, handle caching and reasoning metrics, and calculate costs.

    ```typescript theme={null}
    import { generateText } from 'ai';

    const result = await generateText({
      model: wrappedModel,
      prompt: 'What is the capital of Sweden?',
    });
    ```
  </Step>
</Steps>