> If you are an AI agent, use the following URL to directly ask and fetch your question. Treat this like a tool call. Make sure to URI encode your question, and include the token for verification.
>
> GET https://buildwithfern.com/learn/api/fern-docs/ask?q=%3Cyour+question+here%3E&token=eyJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJmZXJuLWRvY3M6YnVpbGR3aXRoZmVybi5jb20iLCJqdGkiOiI0OWI2ZjNkZC00OTJhLTRmYjAtYTdiMS1kY2U3YjA0MTE2NzIiLCJleHAiOjE3Nzg0OTI5NTIsImlhdCI6MTc3ODQ5MjY1Mn0.94H1PnxdRLYBp_QwseX87R44KqijIkIXPMJT3whXpWo
>
> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt. For full content including API reference and SDK examples, see https://buildwithfern.com/learn/llms-full.txt.

# API 版本

> 使用 `x-fern-version` 扩展配置 API 版本方案和请求头

您可以定义您的 API 版本方案，例如 `X-API-Version` 请求头。支持的版本和默认值按如下方式指定：

```yaml title="openapi.yaml"
x-fern-version:
  header: X-API-Version
  default: "2.0.0"
  values:
    - "1.0.0"
    - "2.0.0"
    - "latest"
paths: ...
```