Structured output and reasoning

Structured output

Pass a provider-compatible response format through the common responseFormat field:

const response = await llm.completion({
  model: "gpt-4.1-mini",
  messages: [{ role: "user", content: "Extract the city from: I live in Kolkata." }],
  responseFormat: {
    type: "json_schema",
    json_schema: {
      name: "location",
      strict: true,
      schema: {
        type: "object",
        properties: { city: { type: "string" } },
        required: ["city"],
        additionalProperties: false,
      },
    },
  },
});

For Anthropic, responseFormat.type must be json_schema, and the schema must be available at responseFormat.json_schema.schema. The adapter translates it to Anthropic's structured-output configuration.

The library returns model output as text. Parse and validate it in your application with the schema library of your choice.

Reasoning effort

const response = await llm.completion({
  model: "reasoning-model",
  messages: [{ role: "user", content: "Solve this problem..." }],
  reasoningEffort: "high",
});

Supported normalized values are none, minimal, low, medium, high, xhigh, max, and auto. Providers may support only a subset. Reasoning text, when exposed by the provider, is normalized to message.reasoning or delta.reasoning.