AI API Request Builder, OpenAI, Anthropic & Gemini curl

This is a deterministic string-construction tool, not an inference engine. It never calls the providers. For each provider it maps your form onto that API's documented request contract, so the command you copy matches the official reference field-for-field. Three things change between providers: the endpoint, the authentication header, and how the system and user messages are shaped.

1. Endpoint and method. OpenAI and OpenAI-compatible providers use POST {base_url}/chat/completions. Anthropic uses POST /v1/messages. Gemini puts the model in the path, /v1beta/models/{model}:generateContent, swapping to :streamGenerateContent when streaming is on.
2. Authentication. OpenAI sends Authorization: Bearer. Anthropic uses x-api-key plus a required anthropic-version: 2023-06-01 header. Gemini uses x-goog-api-key. The key itself is always an environment-variable placeholder, never a literal.
3. Message shaping. OpenAI keeps the system and user turns inside one messages array. Anthropic pulls the system prompt out to a top-level system string (it is not a message role) and requires max_tokens. Gemini nests text under contents[].parts[].text and a separate system_instruction.
4. Parameters.Temperature and token limits map to each API's field name, max_tokens for OpenAI and Anthropic, maxOutputTokens under generationConfig for Gemini. JSON mode becomes response_format (OpenAI) or response_mime_type (Gemini), and is omitted for Anthropic, which has no such flag.
5. Escaping. Your system and user text is JSON-string-escaped, so quotes and newlines never break the body. curl bodies use a single-quoted JSON payload, with any literal single quote escaped for the shell, the copied command runs as-is.

The Python and Node.js tabs each give two variants: a dependency-free raw call (requests /fetch) and the provider's official SDK (openai, anthropic, google-genai). Every snippet carries a comment linking to the exact reference it was built from, and each field maps one-to-one to that reference, so you can trust the copied request without cross-checking three docs sites.

# OpenAI Chat Completions API, https://platform.openai.com/docs/api-reference/chat/create
curl https://api.openai.com/v1/chat/completions \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "gpt-4o",
  "messages": [
    {
      "role": "user",
      "content": "Hello!"
    }
  ],
  "temperature": 0.7,
  "max_tokens": 256
}'

# Anthropic Messages API, https://docs.anthropic.com/en/api/messages
curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "claude-sonnet-5",
  "max_tokens": 512,
  "temperature": 0.5,
  "stream": true,
  "system": "You are terse.",
  "messages": [
    {
      "role": "user",
      "content": "Hi"
    }
  ]
}'

Both blocks are produced by the same function the tool uses, and are checked byte-for-byte against hand-reconciled output in the module's verifyWorkedExamples() cross-check. Switch to the Python or Node.js tab in the tool above to see the equivalent SDK code for either example.

• OpenAI: Chat Completions API reference
• Anthropic: Messages API reference
• Google: Gemini generateContent API reference

Endpoint shapes, headers and body fields on this page were last cross-checked against the official references on 2026-07-09. Provider APIs are versioned; the page is reviewed when a referenced endpoint or required header changes.