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Claude API Request Builder

Build Anthropic Messages API request payloads and cURL commands.

JSON Request Body
{
  "model": "claude-3.5-sonnet",
  "max_tokens": 1024,
  "temperature": 0.7,
  "messages": [
    {
      "role": "user",
      "content": "Hello!"
    }
  ],
  "system": "You are a helpful assistant."
}
cURL Command
curl -X POST 'https://api.anthropic.com/v1/messages' \
  -H 'Content-Type: application/json' \
  -H 'x-api-key: $ANTHROPIC_API_KEY' \
  -H 'anthropic-version: 2023-06-01' \
  -d '{
  "model": "claude-3.5-sonnet",
  "max_tokens": 1024,
  "temperature": 0.7,
  "messages": [
    {
      "role": "user",
      "content": "Hello!"
    }
  ],
  "system": "You are a helpful assistant."
}'
Endpointhttps://api.anthropic.com/v1/messages

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Learn More

guide:claude system promptsguide:openai vs claude

FAQ

How does Claude handle system messages differently from OpenAI?
Claude's Messages API expects the system prompt as a top-level system string, not inside the messages array. This builder handles that extraction automatically.
What headers does Claude require?
Claude requires x-api-key (your Anthropic API key), anthropic-version (e.g. 2023-06-01), and Content-Type: application/json.
Is my Anthropic API key stored?
No. The builder uses a $ANTHROPIC_API_KEY placeholder. Your actual key is never entered or stored here.

Generate ready-to-use JSON request bodies and cURL commands for the Anthropic Claude Messages API. System messages are extracted to the top-level system field automatically. Configure model, temperature, max_tokens, and message turns.