Add usage documentation for undocumented ARM operation templates

website/src/content/docs/docs/howtos/ARM/resource-operations.md

@@ -85,6 +85,22 @@ op get is ArmResourceRead<MyResource>;
 - **get**: The name of the operation passed on to clients.
 - **Resource**: A reference to your resource type.
 
+### Resource Check Existence Operations (HEAD)
+
+The check existence operation uses a HEAD request to efficiently determine whether a resource exists
+without returning the resource body. This is useful when you only need to verify a resource's
+existence and do not need to retrieve its full representation.
+
+```typespec
+op checkExistence is ArmResourceCheckExistence<MyResource>;
+```
+
+| Operation       | TypeSpec                                                    |
+| --------------- | ----------------------------------------------------------- |
+| Check Existence | `checkExistence is ArmResourceCheckExistence<ResourceType>` |
+
+This operation returns a 204 response if the resource exists, or a 404 response if it does not.
+
 ### Resource CreateOrUpdate Operations (PUT)
 
 The CreateOrUpdate operation may be synchronous (The operation may always complete before a response
@@ -117,15 +133,25 @@ PATCH for Resource tags only, a PATCH for all updateable properties, or a custom
 you should choose the patch for all updateable properties, unless you have a very good reason for
 choosing another PATCH operation.
 
-| Operation Description      | TypeSpec                                                         |
-| -------------------------- | ---------------------------------------------------------------- |
-| Sync TagsOnly PATCH        | `update is ArmTagsPatchSync<ResourceType>`                       |
-| Async TagsOnly PATCH       | `update is ArmTagsPatchAsync<ResourceType>`                      |
-| Sync All Properties PATCH  | `update is ArmCustomPatchSync<ResourceType, PatchRequestModel>`  |
-| Async All Properties PATCH | `update is ArmCustomPatchAsync<ResourceType, PatchRequestModel>` |
-
-The ArmTagsPatch\* templates take the resource type as a parameter. The ArmCustomPatch\*
-templates take the resource type and your custom PATCH request type as parameters.
+| Operation Description                       | TypeSpec                                                                |
+| ------------------------------------------- | ----------------------------------------------------------------------- |
+| Sync TagsOnly PATCH                         | `update is ArmTagsPatchSync<ResourceType>`                              |
+| Async TagsOnly PATCH                        | `update is ArmTagsPatchAsync<ResourceType>`                             |
+| Sync Custom Properties PATCH (recommended)  | `update is ArmCustomPatchSync<ResourceType, PatchRequestModel>`         |
+| Async Custom Properties PATCH (recommended) | `update is ArmCustomPatchAsync<ResourceType, PatchRequestModel>`        |
+| Sync Lifecycle PATCH                        | `update is ArmResourcePatchSync<ResourceType, ResourcePropertiesType>`  |
+| Async Lifecycle PATCH                       | `update is ArmResourcePatchAsync<ResourceType, ResourcePropertiesType>` |
+
+The `ArmCustomPatch*` templates are the recommended choice for PATCH operations. They take the
+resource type and your custom PATCH request type as parameters, giving you full control over the
+PATCH schema. The `ArmTagsPatch*` templates take the resource type as a parameter and only allow
+updating ARM tags.
+
+> **Note:** The `ArmResourcePatch*` templates are **not recommended**. They rely on Lifecycle.Update
+> visibility analysis to automatically determine which properties are included in the PATCH schema,
+> but this analysis is only performed by the typespec-autorest emitter and will not be replicated in
+> SDKs generated for the PATCH operation. Instead, spec authors should define a specific PATCH model
+> and use the `ArmCustomPatch*` templates.
 
 ### Resource Delete Operations (DELETE)
 
@@ -160,6 +186,11 @@ Arm Resource list operations return a list of Tracked or Proxy Resources at a pa
 | ------------------ | ----------------------------------------------------------- |
 | ListByParent       | `listByWidget is ArmResourceListByParent<ResourceType>`     |
 | ListBySubscription | `listBySubscription is ArmListBySubscription<ResourceType>` |
+| ListAtScope        | `listAtScope is ArmResourceListAtScope<ResourceType>`       |
+
+The `ArmResourceListAtScope` template is used when the scope of the list operation is determined by
+the `BaseParameters` type parameter. This is useful for resources with custom scope requirements
+that do not fit the standard parent or subscription scopes.
 
 ### Resource Actions (POST)
 
@@ -208,6 +239,22 @@ described in the next section of the document:
 - [Synchronous Resource List Actions](#synchronous-list-action)
 - [Asynchronous List Action](#asynchronous-list-action)
 
+### Provider Actions (POST)
+
+Provider actions are operations that are not scoped to a specific resource instance but instead
+operate at the provider level. These are useful for operations like performing tenant-wide
+configuration or subscription-level actions that are not tied to a particular resource.
+
+| Operation                         | TypeSpec                                                                        |
+| --------------------------------- | ------------------------------------------------------------------------------- |
+| Synchronous Provider Action       | `myAction is ArmProviderActionSync<Request, Response>`                          |
+| Asynchronous Provider Action      | `myAction is ArmProviderActionAsync<Request, Response>`                         |
+| Provider Action with custom scope | `myAction is ArmProviderActionSync<Request, Response, SubscriptionActionScope>` |
+| Provider Action with no request   | `myAction is ArmProviderActionSync<void, Response>`                             |
+
+By default, provider actions use `TenantActionScope`. You can specify a different scope such as
+`SubscriptionActionScope` or `ExtensionResourceActionScope` using the `Scope` template parameter.
+
 ### Check Name Operations
 
 Some services provide operations to check name availability, either location-specific (locally) or