---
lang: en
title: 'API docs: openapi-v3.param'
keywords: LoopBack 4.0, LoopBack 4
sidebar: lb4_sidebar
permalink: /doc/en/lb4/apidocs.openapi-v3.param.html
---

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[Home](./index.md) &gt; [@loopback/openapi-v3](./openapi-v3.md) &gt; [param](./openapi-v3.param.md)

## param namespace

Describe an input parameter of a Controller method. The `@param` decorator takes an argument of `ParameterObject` to define how to map the parameter to OpenAPI specification.

`@param(paramSpec)` must be applied to parameters.

<b>Signature:</b>

```typescript
export declare namespace param 
```

## Variables

|  Variable | Description |
|  --- | --- |
|  [array](./openapi-v3.param.array.md) | Define a parameter of <code>array</code> type. |
|  [header](./openapi-v3.param.header.md) |  |
|  [path](./openapi-v3.param.path.md) |  |
|  [query](./openapi-v3.param.query.md) |  |

## Example


```ts
class MyController {
  @get('/')
  list(
    @param(offsetSpec) offset?: number,
    @param(pageSizeSpec) pageSize?: number,
  ) {}
}

```