---
title: Direct REST API Usage
product: vercel
url: /docs/ai-gateway/sdks-and-apis/openai-chat-completions/rest-api
type: conceptual
prerequisites:
  - /docs/ai-gateway/sdks-and-apis/openai-chat-completions
  - /docs/ai-gateway/sdks-and-apis
related:
  []
summary: Use the AI Gateway API directly without client libraries using curl and fetch.
install_vercel_plugin: npx plugins add vercel/vercel-plugin
---

# Direct REST API Usage

If you prefer to use the AI Gateway API directly without the OpenAI client libraries, you can make HTTP requests using any HTTP client. Here are examples using `curl` and JavaScript's `fetch` API:

### List models

#### cURL

```bash filename="list-models.sh"
curl -X GET "https://ai-gateway.vercel.sh/v1/models" \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "Content-Type: application/json"
```

#### JavaScript

```javascript filename="list-models.js"
const response = await fetch('https://ai-gateway.vercel.sh/v1/models', {
  method: 'GET',
  headers: {
    Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
    'Content-Type': 'application/json',
  },
});

const models = await response.json();
console.log(models);
```

### Basic chat completion

#### cURL

```bash filename="chat-completion.sh"
curl -X POST "https://ai-gateway.vercel.sh/v1/chat/completions" \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-opus-4.6",
    "messages": [
      {
        "role": "user",
        "content": "Write a one-sentence bedtime story about a unicorn."
      }
    ],
    "stream": false
  }'
```

#### JavaScript

```javascript filename="chat-completion.js"
const response = await fetch(
  'https://ai-gateway.vercel.sh/v1/chat/completions',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      model: 'anthropic/claude-opus-4.6',
      messages: [
        {
          role: 'user',
          content: 'Write a one-sentence bedtime story about a unicorn.',
        },
      ],
      stream: false,
    }),
  },
);

const result = await response.json();
console.log(result);
```

### Streaming chat completion

#### cURL

```bash filename="streaming-chat.sh"
curl -X POST "https://ai-gateway.vercel.sh/v1/chat/completions" \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-opus-4.6",
    "messages": [
      {
        "role": "user",
        "content": "Write a one-sentence bedtime story about a unicorn."
      }
    ],
    "stream": true
  }' \
  --no-buffer
```

#### JavaScript

```javascript filename="streaming-chat.js"
const response = await fetch(
  'https://ai-gateway.vercel.sh/v1/chat/completions',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      model: 'anthropic/claude-opus-4.6',
      messages: [
        {
          role: 'user',
          content: 'Write a one-sentence bedtime story about a unicorn.',
        },
      ],
      stream: true,
    }),
  },
);

const reader = response.body.getReader();
const decoder = new TextDecoder();

while (true) {
  const { done, value } = await reader.read();
  if (done) break;

  const chunk = decoder.decode(value);
  const lines = chunk.split('\n');

  for (const line of lines) {
    if (line.startsWith('data: ')) {
      const data = line.slice(6);
      if (data === '[DONE]') {
        console.log('Stream complete');
        break;
      } else if (data.trim()) {
        const parsed = JSON.parse(data);
        const content = parsed.choices?.[0]?.delta?.content;
        if (content) {
          process.stdout.write(content);
        }
      }
    }
  }
}
```

### Image analysis

#### cURL

```bash filename="image-analysis.sh"
# First, convert your image to base64
IMAGE_BASE64=$(base64 -i ./path/to/image.png)

curl -X POST "https://ai-gateway.vercel.sh/v1/chat/completions" \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-opus-4.6",
    "messages": [
      {
        "role": "user",
        "content": [
          {
            "type": "text",
            "text": "Describe this image in detail."
          },
          {
            "type": "image_url",
            "image_url": {
              "url": "data:image/png;base64,'"$IMAGE_BASE64"'",
              "detail": "auto"
            }
          }
        ]
      }
    ],
    "stream": false
  }'
```

#### JavaScript

```javascript filename="image-analysis.js"
import fs from 'node:fs';

// Read the image file as base64
const imageBuffer = fs.readFileSync('./path/to/image.png');
const imageBase64 = imageBuffer.toString('base64');

const response = await fetch(
  'https://ai-gateway.vercel.sh/v1/chat/completions',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      model: 'anthropic/claude-opus-4.6',
      messages: [
        {
          role: 'user',
          content: [
            { type: 'text', text: 'Describe this image in detail.' },
            {
              type: 'image_url',
              image_url: {
                url: `data:image/png;base64,${imageBase64}`,
                detail: 'auto',
              },
            },
          ],
        },
      ],
      stream: false,
    }),
  },
);

const result = await response.json();
console.log(result);
```

### Tool calls

#### cURL

```bash filename="tool-calls.sh"
curl -X POST "https://ai-gateway.vercel.sh/v1/chat/completions" \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-opus-4.6",
    "messages": [
      {
        "role": "user",
        "content": "What is the weather like in San Francisco?"
      }
    ],
    "tools": [
      {
        "type": "function",
        "function": {
          "name": "get_weather",
          "description": "Get the current weather in a given location",
          "parameters": {
            "type": "object",
            "properties": {
              "location": {
                "type": "string",
                "description": "The city and state, e.g. San Francisco, CA"
              },
              "unit": {
                "type": "string",
                "enum": ["celsius", "fahrenheit"],
                "description": "The unit for temperature"
              }
            },
            "required": ["location"]
          }
        }
      }
    ],
    "tool_choice": "auto",
    "stream": false
  }'
```

#### JavaScript

```javascript filename="tool-calls.js"
const response = await fetch(
  'https://ai-gateway.vercel.sh/v1/chat/completions',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      model: 'anthropic/claude-opus-4.6',
      messages: [
        {
          role: 'user',
          content: 'What is the weather like in San Francisco?',
        },
      ],
      tools: [
        {
          type: 'function',
          function: {
            name: 'get_weather',
            description: 'Get the current weather in a given location',
            parameters: {
              type: 'object',
              properties: {
                location: {
                  type: 'string',
                  description: 'The city and state, e.g. San Francisco, CA',
                },
                unit: {
                  type: 'string',
                  enum: ['celsius', 'fahrenheit'],
                  description: 'The unit for temperature',
                },
              },
              required: ['location'],
            },
          },
        },
      ],
      tool_choice: 'auto',
      stream: false,
    }),
  },
);

const result = await response.json();
console.log(result);
```

### Provider options

#### cURL

```bash filename="provider-options.sh"
curl -X POST "https://ai-gateway.vercel.sh/v1/chat/completions" \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-opus-4.6",
    "messages": [
      {
        "role": "user",
        "content": "Tell me the history of the San Francisco Mission-style burrito in two paragraphs."
      }
    ],
    "stream": false,
    "providerOptions": {
      "gateway": {
        "order": ["vertex", "anthropic"]
      }
    }
  }'
```

#### JavaScript

```javascript filename="provider-options.js"
const response = await fetch(
  'https://ai-gateway.vercel.sh/v1/chat/completions',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      model: 'anthropic/claude-opus-4.6',
      messages: [
        {
          role: 'user',
          content:
            'Tell me the history of the San Francisco Mission-style burrito in two paragraphs.',
        },
      ],
      stream: false,
      providerOptions: {
        gateway: {
          order: ['vertex', 'anthropic'], // Try Vertex AI first, then Anthropic
        },
      },
    }),
  },
);

const result = await response.json();
console.log(result);
```


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