tool use

Allows Claude to call developer-defined functions. Claude decides when to invoke tools and with what arguments based on the user's request.

Syntax

claude-api

{ tools: [{ name, description, input_schema }], messages }

Example

claude-api

const response = await client.messages.create({
  model: "claude-opus-4-5",
  max_tokens: 1024,
  tools: [{
    name: "get_weather",
    description: "Get weather for a city",
    input_schema: { type: "object", properties: { city: { type: "string" } }, required: ["city"] }
  }],
  messages: [{ role: "user", content: "What is the weather in Paris?" }]
});