# Modules

Source: `src/domains/ModulesDomain.ts`. Calls an installed module function as
the signed-in player through `POST /sdk/v1/modules/{module}/{fn}`.

```ts
client.modules.call(module: string, fn: string, args?: unknown): Promise<CallModuleFunctionClientResponse>
// CallModuleFunctionClientResponse = { result?: unknown }
```

```ts
const { result } = await client.modules.call('my_module', 'hello', { name: 'Bob' });
```

`args` is sent as `{ args }`. The response carries only `result`; console
output and the kernel call log stay on the platform dry run.

A business error raised by the module rejects with `RudderHttpError`
(`status` 422, body `{ error, code, requestId }`) whose `code` is the
module's own open string code; there are no generated constants for it. A
trap is a 500 and a timeout a 504, both without details.

```ts
try {
  await client.modules.call('my_module', 'hello');
} catch (error) {
  if (error instanceof RudderHttpError && error.status === 422) {
    console.warn(error.code); // module-defined
  }
}
```