Provide a hook that allows modules to declare Field Modules they provide.

modules/farm/farm_client/farm_client.api.php

@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * @file
+ * Hooks provided by farm_client.
+ *
+ * This file contains no working PHP code; it exists to provide additional
+ * documentation for doxygen as well as to document hooks in the standard
+ * Drupal manner.
+ */
+
+/**
+ * @defgroup farm_client Farm client module integrations.
+ *
+ * Module integrations with the farm_client module.
+ */
+
+/**
+ * @defgroup farm_client_hooks Farm client's hooks
+ * @{
+ * Hooks that can be implemented by other modules in order to extend farm_client.
+ */
+
+/**
+ * Provide information about client modules that this module provides.
+ *
+ * @return array
+ *   Returns an array of client module information.
+ */
+function hook_farm_client_modules() {
+  return array(
+    array(
+      'name' => 'weather',
+      'label' => t('Weather'),
+      'js' => drupal_get_path('module', 'farm_weather') . '/src/FieldModule/Weather/weather.js',
+    ),
+  );
+}
+
+/**
+ * @}
+ */

modules/farm/farm_client/farm_client.module

@@ -19,3 +19,21 @@ function farm_client_farm_api_oauth2_client() {
 
   return $clients;
 }
+
+/**
+ * Implements hook_farm_info().
+ */
+function farm_client_farm_info() {
+
+  // Ask modules for client module info.
+  $client_modules = module_invoke_all('farm_client_modules');
+
+  // Add the client module info to /farm.json.
+  $info = array();
+  if (!empty($client_modules)) {
+    $info['client'] = array(
+      'modules' => $client_modules,
+    );
+  }
+  return $info;
+}