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<h1>Chat Completions API</h1>
<p>The Chat Completions API allows you to generate conversational responses using Claude models.</p>
<h2>Authentication</h2>
<p>All API requests require authentication using an API key:</p>
<pre><code class="language-bash">curl https://api.anthropic.com/v1/messages \
-H "Authorization: Bearer $API_KEY" \
-H "Content-Type: application/json"</code></pre>
<h2>Request Format</h2>
<p>Send a POST request to <code>/v1/messages</code> with the following structure:</p>
<pre><code class="language-json">{
"model": "claude-3-sonnet-20240229",
"max_tokens": 1000,
"messages": [
{
"role": "user",
"content": "Hello, Claude!"
}
]
}</code></pre>
<h3>Parameters</h3>
<table>
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<th>Parameter</th>
<th>Type</th>
<th>Required</th>
<th>Description</th>
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<td><code>model</code></td>
<td>string</td>
<td>Yes</td>
<td>The model to use for completion</td>
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<tr>
<td><code>messages</code></td>
<td>array</td>
<td>Yes</td>
<td>List of messages in the conversation</td>
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<td><code>max_tokens</code></td>
<td>integer</td>
<td>Yes</td>
<td>Maximum number of tokens to generate</td>
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</table>
<div class="note">
<h4>Note</h4>
<p>The API uses token-based pricing. Each request consumes tokens based on input and output length.</p>
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<h2>Response Format</h2>
<p>The API returns a JSON response:</p>
<pre><code class="language-json">{
"id": "msg_123",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "Hello! How can I help you today?"
}
],
"model": "claude-3-sonnet-20240229",
"usage": {
"input_tokens": 10,
"output_tokens": 25
}
}</code></pre>
<div class="warning">
<p>⚠️ Rate limits apply to all API calls. See the rate limiting documentation for details.</p>
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<h3>Quick Links</h3>
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<li><a href="/docs/quickstart">Quickstart</a></li>
<li><a href="/docs/models">Models</a></li>
<li><a href="/docs/pricing">Pricing</a></li>
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