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

# Getting started

> First steps with Anthropic middleware for tracking AI costs.

## Installation

```bash npm theme={null}
npm install @ai-billing/anthropic @ai-billing/core @ai-sdk/anthropic ai
```

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

```bash yarn theme={null}
yarn add @ai-billing/anthropic @ai-billing/core @ai-sdk/anthropic ai
```

## Overview

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

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

## Usage

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

**1. Initialize the Anthropic provider**

First, set up the Anthropic provider using your API key.

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

const anthropic = createAnthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});
```

**2. Define model pricing**

Set up a price resolver to define the costs for the models you'll be using. For Anthropic, you can specify costs for both standard prompt/completion tokens and cached tokens (`inputCacheReadTokens` and `inputCacheWriteTokens`).

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

const priceResolver = createObjectPriceResolver({
  'claude-sonnet-4-6': {
    promptTokens: 0.000003,
    completionTokens: 0.000015,
    inputCacheReadTokens: 0.0000003,
    inputCacheWriteTokens: 0.00000375,
  },
});
```

**3. Create the billing middleware**

Initialize the Anthropic 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 { createAnthropicMiddleware } from '@ai-billing/anthropic';
import { consoleDestination } from '@ai-billing/core';

const billingMiddleware = createAnthropicMiddleware({
  destinations: [consoleDestination()],
  priceResolver: priceResolver,
});
```

**4. Wrap the model**

Use `wrapLanguageModel` from the `ai` package to apply the billing middleware to your Anthropic model.

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

const wrappedModel = wrapLanguageModel({
  model: anthropic('claude-sonnet-4-6'),
  middleware: billingMiddleware,
});
```

**5. 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 metrics, and calculate costs.

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

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


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