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

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, 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 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 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 source and generated via 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, which scrapes and formats provider data. This string is rendered into the final README.md through the template system defined in 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

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

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 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, README.md, and 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 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. 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 script, which generates the markdown documentation section containing **Limits:** [$5/month]. This value is rendered into README.md through the template system defined in src/README_template.md, ensuring the pricing data remains accurate in the generated documentation.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}