# How Vercel AI Gateway Routes Requests to Providers and Its $5/Month Limitations

> Learn how Vercel AI Gateway routes LLM requests to providers using model prefixes and understand the $5 monthly credit limit before pay-as-you-go rates apply.

- Repository: [Jun Siang Cheah/free-llm-api-resources](https://github.com/cheahjs/free-llm-api-resources)
- Tags: deep-dive
- Published: 2026-05-07

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**Vercel AI Gateway acts as a unified proxy that routes requests to LLM providers based on model name prefixes (e.g., `openai/gpt-4`), while the free tier provides $5 in monthly credits before transitioning to standard pay-as-you-go rates.**

The `cheahjs/free-llm-api-resources` repository tracks multiple methods for accessing large language models without upfront costs, including the **Vercel AI Gateway** routing architecture. This gateway simplifies multi-provider AI development by offering a single endpoint that automatically directs traffic to OpenAI, Anthropic, and other supported services based on configuration files and model identifiers.

## How Vercel AI Gateway Routes Requests to Providers

Vercel AI Gateway functions as a lightweight proxy layer that abstracts provider-specific API differences. According to the repository's documentation in [`README.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/README.md), the system uses a combination of configuration files and model string parsing to determine routing destinations.

### Provider Configuration via vercel.json

Gateway behavior is controlled through a [`vercel.json`](https://github.com/cheahjs/free-llm-api-resources/blob/main/vercel.json) configuration file or environment variables such as `VERCEL_AI_PROVIDER` set in the Vercel dashboard. As implemented in the repository's [`src/pull_available_models.py`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/pull_available_models.py) generation logic, each provider entry includes the provider name (e.g., `openai`, `anthropic`, `cohere`) and associated authentication credentials. Vercel reads these values to establish authenticated connections with each backend service.

The configuration supports multiple providers simultaneously, allowing a single deployment to proxy requests to diverse LLM services without code changes.

### Model Prefix Routing Mechanism

When a request hits the gateway endpoint at `https://<your-project>.vercel.app/api/ai`, Vercel extracts the **model identifier** from the JSON payload. The gateway parses the prefix before the forward slash—such as `openai/` in `openai/gpt-4` or `anthropic/` in `anthropic/claude-3-opus-20240229`—to select the appropriate provider.

If the prefix matches a configured provider, Vercel forwards the request to that provider's official API endpoint, automatically injecting the stored API key and translating request formats as needed. Requests with unrecognized model prefixes return a `400 Bad Request` error, indicating the provider is not configured.

### Unified Request Normalization

The gateway normalizes provider-specific payloads into a consistent schema based on the OpenAI API format. This normalization handles differences in token limits, streaming formats, and response structures, allowing client code to remain provider-agnostic.

## The $5/Month Free Tier Limitations

The Vercel AI Gateway free tier operates on a **$5 monthly credit system** rather than request-based limits. As documented in the [`README.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/README.md) source and generated via [`src/pull_available_models.py`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/pull_available_models.py), this credit applies to all provider usage routed through the gateway.

### Credit Allocation and Billing

Each Vercel account receives $5 in usage credits per calendar month for AI Gateway consumption. Once these credits exhaust, the service transitions to **pay-as-you-go billing** at the provider's standard API rates—Vercel does not add additional markup to the underlying provider costs. The credit counter resets at the beginning of each billing cycle.

### Source Code Documentation of Limits

The specific limit notation `**Limits:** [$5/month]` is programmatically inserted into the documentation by [`src/pull_available_models.py`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/pull_available_models.py), which scrapes and formats provider data. This string is rendered into the final [`README.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/README.md) through the template system defined in [`src/README_template.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/README_template.md), ensuring the repository accurately reflects Vercel's current pricing structure.

## Code Implementation Examples

The following examples demonstrate how to interact with the gateway using model prefixes that trigger the routing logic.

### Python Request Example

```python
import requests
import os

url = "https://my-project.vercel.app/api/ai"
payload = {
    "model": "openai/gpt-4o-mini",  # Routes to OpenAI provider

    "messages": [{"role": "user", "content": "Explain Vercel AI Gateway routing"}],
    "max_tokens": 200,
}
headers = {"Authorization": f"Bearer {os.getenv('VERCEL_AI_TOKEN')}"}

response = requests.post(url, json=payload, headers=headers)
print(response.json())

```

### JavaScript SDK Implementation

```javascript
import { createAi } from '@vercel/ai';

const ai = createAi({
  endpoint: '/api/ai',  // Vercel AI Gateway endpoint
});

async function routeToAnthropic() {
  const response = await ai.chat.completions.create({
    model: 'anthropic/claude-3-haiku-20240307',  // Routes to Anthropic
    messages: [{ role: 'user', content: 'What are the $5/month limitations?' }],
  });
  console.log(response);
}

routeToAnthropic();

```

## Summary

- **Vercel AI Gateway** uses model name prefix parsing (e.g., `provider/model-name`) to route requests to the appropriate LLM API endpoint.
- Configuration occurs via [`vercel.json`](https://github.com/cheahjs/free-llm-api-resources/blob/main/vercel.json) or environment variables like `VERCEL_AI_PROVIDER`, with credentials stored securely in the Vercel platform.
- The **$5/month free tier** provides usage credits that reset monthly; excess consumption bills at standard provider rates without additional gateway fees.
- Source files [`src/pull_available_models.py`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/pull_available_models.py), [`README.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/README.md), and [`src/README_template.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/README_template.md) in the `cheahjs/free-llm-api-resources` repository document these routing rules and limitations.
- Both REST API and JavaScript SDK approaches support provider-agnostic code through the gateway's request normalization.

## Frequently Asked Questions

### How does Vercel AI Gateway determine which provider to use for a request?

The gateway examines the `model` parameter in the request payload and splits the string at the forward slash. The prefix (e.g., `openai`, `anthropic`) maps to a configured provider in your [`vercel.json`](https://github.com/cheahjs/free-llm-api-resources/blob/main/vercel.json) file or environment variables, directing the request to the corresponding backend API.

### What happens when I exceed the $5 monthly credit limit?

Once the $5 credit exhausts, Vercel automatically switches to pay-as-you-go billing. You are charged directly at the underlying provider's standard API rates (e.g., OpenAI's or Anthropic's listed pricing), with no additional markup from Vercel for the gateway service.

### Can I use multiple LLM providers with a single Vercel AI Gateway deployment?

Yes. The gateway supports simultaneous configuration of multiple providers in [`vercel.json`](https://github.com/cheahjs/free-llm-api-resources/blob/main/vercel.json). You can route different requests to OpenAI, Anthropic, Cohere, or other supported services simply by changing the model prefix in your API calls, without redeploying your application.

### Where is the $5/month limitation documented in the source code?

The limitation appears in the repository's [`src/pull_available_models.py`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/pull_available_models.py) script, which generates the markdown documentation section containing `**Limits:** [$5/month]`. This value is rendered into [`README.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/README.md) through the template system defined in [`src/README_template.md`](https://github.com/cheahjs/free-llm-api-resources/blob/main/src/README_template.md), ensuring the pricing data remains accurate in the generated documentation.