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# Customize parameter names

> Use `x-fern-parameter-name` to customize query parameter, header and path parameter naming.

The `x-fern-parameter-name` extension allows you to customize the variable names of parameters in your generated SDKs.

## Headers

In the example below, the header `X-API-Version` is renamed to `version` in the
generated SDK. The rename makes the SDK more human readable.

```yaml {8}
paths:
  "/user":
    get:
      operationId: list_user
      parameters:
        - in: header
          name: X-API-Version
          x-fern-parameter-name: version
          schema:
            type: string
          required: true
```

## Query parameters

In the example below, the query parameter `q` is renamed to `search_terms` in the
generated SDK. The rename makes the parameter more approachable for end users.

```yaml {8}
paths:
  "/user/search":
    get:
      operationId: search_user
      parameters:
        - in: query
          name: q
          x-fern-parameter-name: search_terms
          schema:
            type: string
          required: false
```

## Path parameters

In the example below, the path parameter `userId` is renamed to `id` in the
generated SDK. The rename makes the SDK less verbose.

```yaml {8}
paths:
  "/user/{userId}":
    get:
      operationId: get_user
      parameters:
        - in: path
          name: userId
          x-fern-parameter-name: id
          schema:
            type: string
          required: false
```

Renaming a path parameter is also how you resolve a naming collision. A path parameter can't share a name with another request property (a body property, query parameter, or header), including after camelCase normalization. `fern check` reports these collisions; set `x-fern-parameter-name` on the path parameter to rename it and resolve the collision.

> Use `x-fern-parameter-name` to customize query parameter, header and path parameter naming.