Token Counting & File Management

Anthropic provides the /v1/messages/count_tokens endpoint to calculate the exact token consumption of a request (including system prompts, tools, images, and documents) before sending it for inference. This endpoint is free of charge and creates no Message objects.

const count = await anthropic.messages.count_tokens({
  model: "claude-3-7-sonnet-20250219",
  messages: [{ role: "user", content: "Your prompt here..." }],
  system: "Your system instructions..."
});
console.log("Input tokens:", count.input_tokens);