diff --git a/.chronus/changes/update_doc-2024-1-18-15-55-46.md b/.chronus/changes/update_doc-2024-1-18-15-55-46.md
new file mode 100644
index 0000000000..594f8a85f6
--- /dev/null
+++ b/.chronus/changes/update_doc-2024-1-18-15-55-46.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+Update doc for `@access` and `@usage`
\ No newline at end of file
diff --git a/docs/libraries/typespec-client-generator-core/reference/decorators.md b/docs/libraries/typespec-client-generator-core/reference/decorators.md
index 0e32fe7902..5c9b0c6afe 100644
--- a/docs/libraries/typespec-client-generator-core/reference/decorators.md
+++ b/docs/libraries/typespec-client-generator-core/reference/decorators.md
@@ -10,7 +10,17 @@ toc_max_heading_level: 3
 
 ### `@access` {#@Azure.ClientGenerator.Core.access}
 
-Set access for operations, models and enums. All models that are only used in operations with access "internal" will be implicitly set to access "internal".
+Set explicit access for operations, models and enums.
+When setting access for models,
+the access info wll not be propagated to models' properties, base models or sub models.
+When setting access for an operation,
+it will influence the access info for models/enums that are used by this operation.
+Models/enums that are used in any operations with `@access(Access.public)` will be implicitly set to access "public"
+Models/enums that are only used in operations with `@access(Access.internal)` will be implicitly set to access "internal".
+This influence will be propagated to models' properties, parent models, discriminated sub models.
+But this influence will be override by `@usage` decorator on models/enums directly.
+If an operation/model/enum has no `@access` decorator and is not influenced by any operation with `@access` decorator,
+the access result is undefined.
 
 ```typespec
 @Azure.ClientGenerator.Core.access(value: EnumMember, scope?: valueof string)
@@ -29,15 +39,114 @@ Set access for operations, models and enums. All models that are only used in op
 
 #### Examples
 
+##### Set access
+
 ```typespec
+// Access.internal
 @access(Access.internal)
 model ModelToHide {
 prop: valueof string
 }
+// Access.internal
 @access(Access.internal)
 op test: void;
 ```
 
+##### Access propagation
+
+```typespec
+// Access.internal
+@discriminator("kind")
+model Fish {
+  age: int32;
+}
+
+// Access.internal
+@discriminator("sharktype")
+model Shark extends Fish {
+  kind: "shark";
+  origin: Origin;
+}
+
+// Access.internal
+model Salmon extends Fish {
+  kind: "salmon";
+}
+
+// Access.internal
+model SawShark extends Shark {
+  sharktype: "saw";
+}
+
+// Access.internal
+model Origin {
+  country: string;
+  city: string;
+  manufacture: string;
+}
+
+// Access.internal
+@get
+@access(Access.internal)
+op getModel(): Fish;
+```
+
+##### Access influence from operation
+
+```typespec
+// Access.internal
+model Test1 {}
+
+// Access.internal
+@access(Access.internal)
+@route("/func1")
+op func1(@body body: Test1): void;
+
+// undefined
+model Test2 {}
+
+// undefined
+@route("/func2")
+op func2(@body body: Test2): void;
+
+// Access.public
+model Test3 {}
+
+// Access.public
+@access(Access.public)
+@route("/func3")
+op func3(@body body: Test3): void;
+
+// undefined
+model Test4 {}
+
+// Access.internal
+@access(Access.internal)
+@route("/func4")
+op func4(@body body: Test4): void;
+
+// undefined
+@route("/func5")
+op func5(@body body: Test4): void;
+
+// Access.public
+model Test5 {}
+
+// Access.internal
+@access(Access.internal)
+@route("/func6")
+op func6(@body body: Test5): void;
+
+// undefined
+@route("/func7")
+op func7(@body body: Test5): void;
+
+// Access.public
+@access(Access.public)
+@route("/func8")
+op func8(@body body: Test5): void;
+```
+
 ### `@client` {#@Azure.ClientGenerator.Core.client}
 
 Create a ClientGenerator.Core client out of a namespace or interface
@@ -341,8 +450,18 @@ op test: void;
 
 ### `@usage` {#@Azure.ClientGenerator.Core.usage}
 
-Expand usage for models/enums. A model's default usage info is always calculated by the operations that use it.
-You could use this decorator to expand the default usage info. (e.g. append Usage.input by
+Expand usage for models/enums.
+A model/enum's default usage info is always calculated by the operations that use it.
+You could use this decorator to expand the default usage info.
+For example, with operation definition `op test(): OutputModel`,
+the model `OutputModel` has default usage `Usage.output`.
+After adding decorator `@@usage(OutputModel, Usage.input)`,
+the final usage result for `OutputModel` is `Usage.input | Usage.output`.
+The calculation of default usage info for models will be propagated to models' properties,
+parent models, discriminated sub models.
+But the expanded usage from `@usage` decorator will not be propagated.
+If you want to do any customization for the usage of a model,
+you need to take care of all related models/enums.
 
 ```typespec
 @Azure.ClientGenerator.Core.usage(value: EnumMember | Union, scope?: valueof string)
@@ -361,9 +480,52 @@ You could use this decorator to expand the default usage info. (e.g. append Usag
 
 #### Examples
 
+##### Expand usage for model
+
 ```typespec
-@usage(Usage.input | Usage.output)
-model InputAndOutPutModel {
+op test(): OutputModel;
+
+// usage result for `OutputModel` is `Usage.input | Usage.output`
+@usage(Usage.input)
+model OutputModel {
   prop: string;
 }
 ```
+
+##### Propagation of usage
+
+```typespec
+// Usage.output
+@discriminator("kind")
+model Fish {
+  age: int32;
+}
+
+// Usage.input | Usage.output
+@discriminator("sharktype")
+@usage(Usage.input)
+model Shark extends Fish {
+  kind: "shark";
+  origin: Origin;
+}
+
+// Usage.output
+model Salmon extends Fish {
+  kind: "salmon";
+}
+
+// Usage.output
+model SawShark extends Shark {
+  sharktype: "saw";
+}
+
+// Usage.output
+model Origin {
+  country: string;
+  city: string;
+  manufacture: string;
+}
+
+@get
+op getModel(): Fish;
+```
diff --git a/packages/typespec-client-generator-core/README.md b/packages/typespec-client-generator-core/README.md
index 0e7e05b638..a60bb1bba4 100644
--- a/packages/typespec-client-generator-core/README.md
+++ b/packages/typespec-client-generator-core/README.md
@@ -27,7 +27,17 @@ npm install @azure-tools/typespec-client-generator-core
 
 #### `@access`
 
-Set access for operations, models and enums. All models that are only used in operations with access "internal" will be implicitly set to access "internal".
+Set explicit access for operations, models and enums.
+When setting access for models,
+the access info wll not be propagated to models' properties, base models or sub models.
+When setting access for an operation,
+it will influence the access info for models/enums that are used by this operation.
+Models/enums that are used in any operations with `@access(Access.public)` will be implicitly set to access "public"
+Models/enums that are only used in operations with `@access(Access.internal)` will be implicitly set to access "internal".
+This influence will be propagated to models' properties, parent models, discriminated sub models.
+But this influence will be override by `@usage` decorator on models/enums directly.
+If an operation/model/enum has no `@access` decorator and is not influenced by any operation with `@access` decorator,
+the access result is undefined.
 
 ```typespec
 @Azure.ClientGenerator.Core.access(value: EnumMember, scope?: valueof string)
@@ -46,15 +56,114 @@ Set access for operations, models and enums. All models that are only used in op
 
 ##### Examples
 
+###### Set access
+
 ```typespec
+// Access.internal
 @access(Access.internal)
 model ModelToHide {
 prop: valueof string
 }
+// Access.internal
 @access(Access.internal)
 op test: void;
 ```
 
+###### Access propagation
+
+```typespec
+// Access.internal
+@discriminator("kind")
+model Fish {
+  age: int32;
+}
+
+// Access.internal
+@discriminator("sharktype")
+model Shark extends Fish {
+  kind: "shark";
+  origin: Origin;
+}
+
+// Access.internal
+model Salmon extends Fish {
+  kind: "salmon";
+}
+
+// Access.internal
+model SawShark extends Shark {
+  sharktype: "saw";
+}
+
+// Access.internal
+model Origin {
+  country: string;
+  city: string;
+  manufacture: string;
+}
+
+// Access.internal
+@get
+@access(Access.internal)
+op getModel(): Fish;
+```
+
+###### Access influence from operation
+
+```typespec
+// Access.internal
+model Test1 {}
+
+// Access.internal
+@access(Access.internal)
+@route("/func1")
+op func1(@body body: Test1): void;
+
+// undefined
+model Test2 {}
+
+// undefined
+@route("/func2")
+op func2(@body body: Test2): void;
+
+// Access.public
+model Test3 {}
+
+// Access.public
+@access(Access.public)
+@route("/func3")
+op func3(@body body: Test3): void;
+
+// undefined
+model Test4 {}
+
+// Access.internal
+@access(Access.internal)
+@route("/func4")
+op func4(@body body: Test4): void;
+
+// undefined
+@route("/func5")
+op func5(@body body: Test4): void;
+
+// Access.public
+model Test5 {}
+
+// Access.internal
+@access(Access.internal)
+@route("/func6")
+op func6(@body body: Test5): void;
+
+// undefined
+@route("/func7")
+op func7(@body body: Test5): void;
+
+// Access.public
+@access(Access.public)
+@route("/func8")
+op func8(@body body: Test5): void;
+```
+
 #### `@client`
 
 Create a ClientGenerator.Core client out of a namespace or interface
@@ -358,8 +467,18 @@ op test: void;
 
 #### `@usage`
 
-Expand usage for models/enums. A model's default usage info is always calculated by the operations that use it.
-You could use this decorator to expand the default usage info. (e.g. append Usage.input by
+Expand usage for models/enums.
+A model/enum's default usage info is always calculated by the operations that use it.
+You could use this decorator to expand the default usage info.
+For example, with operation definition `op test(): OutputModel`,
+the model `OutputModel` has default usage `Usage.output`.
+After adding decorator `@@usage(OutputModel, Usage.input)`,
+the final usage result for `OutputModel` is `Usage.input | Usage.output`.
+The calculation of default usage info for models will be propagated to models' properties,
+parent models, discriminated sub models.
+But the expanded usage from `@usage` decorator will not be propagated.
+If you want to do any customization for the usage of a model,
+you need to take care of all related models/enums.
 
 ```typespec
 @Azure.ClientGenerator.Core.usage(value: EnumMember | Union, scope?: valueof string)
@@ -378,9 +497,52 @@ You could use this decorator to expand the default usage info. (e.g. append Usag
 
 ##### Examples
 
+###### Expand usage for model
+
 ```typespec
-@usage(Usage.input | Usage.output)
-model InputAndOutPutModel {
+op test(): OutputModel;
+
+// usage result for `OutputModel` is `Usage.input | Usage.output`
+@usage(Usage.input)
+model OutputModel {
   prop: string;
 }
 ```
+
+###### Propagation of usage
+
+```typespec
+// Usage.output
+@discriminator("kind")
+model Fish {
+  age: int32;
+}
+
+// Usage.input | Usage.output
+@discriminator("sharktype")
+@usage(Usage.input)
+model Shark extends Fish {
+  kind: "shark";
+  origin: Origin;
+}
+
+// Usage.output
+model Salmon extends Fish {
+  kind: "salmon";
+}
+
+// Usage.output
+model SawShark extends Shark {
+  sharktype: "saw";
+}
+
+// Usage.output
+model Origin {
+  country: string;
+  city: string;
+  manufacture: string;
+}
+
+@get
+op getModel(): Fish;
+```
diff --git a/packages/typespec-client-generator-core/lib/decorators.tsp b/packages/typespec-client-generator-core/lib/decorators.tsp
index 7923655bd9..b680a0dc90 100644
--- a/packages/typespec-client-generator-core/lib/decorators.tsp
+++ b/packages/typespec-client-generator-core/lib/decorators.tsp
@@ -170,18 +170,68 @@ enum Usage {
 }
 
 /**
- * Expand usage for models/enums. A model's default usage info is always calculated by the operations that use it.
- * You could use this decorator to expand the default usage info. (e.g. append Usage.input by @usage(Usage.input) to the calculated usage Usage.output becomes Usage.input | Usage.output)
+ * Expand usage for models/enums.
+ * A model/enum's default usage info is always calculated by the operations that use it.
+ * You could use this decorator to expand the default usage info.
+ * For example, with operation definition `op test(): OutputModel`,
+ * the model `OutputModel` has default usage `Usage.output`.
+ * After adding decorator `@@usage(OutputModel, Usage.input)`,
+ * the final usage result for `OutputModel` is `Usage.input | Usage.output`.
+ * The calculation of default usage info for models will be propagated to models' properties,
+ * parent models, discriminated sub models.
+ * But the expanded usage from `@usage` decorator will not be propagated.
+ * If you want to do any customization for the usage of a model,
+ * you need to take care of all related models/enums.
  * @param value The usage info you want to set for this model.
  * @param scope The language scope you want this decorator to apply to. If not specified, will apply to all language emitters
  *
- * @example
+ * @example Expand usage for model
  * ```typespec
- * @usage(Usage.input | Usage.output)
- * model InputAndOutPutModel {
+ * op test(): OutputModel;
+ *
+ * // usage result for `OutputModel` is `Usage.input | Usage.output`
+ * @usage(Usage.input)
+ * model OutputModel {
  *   prop: string
  * }
  * ```
+ *
+ * @example Propagation of usage
+ * ```typespec
+ * // Usage.output
+ * @discriminator("kind")
+ * model Fish {
+ *   age: int32;
+ * }
+ *
+ * // Usage.input | Usage.output
+ * @discriminator("sharktype")
+ * @usage(Usage.input)
+ * model Shark extends Fish {
+ *   kind: "shark";
+ *   origin: Origin;
+ * }
+ *
+ * // Usage.output
+ * model Salmon extends Fish {
+ *   kind: "salmon";
+ * }
+ *
+ * // Usage.output
+ * model SawShark extends Shark {
+ *   sharktype: "saw";
+ * }
+ *
+ * // Usage.output
+ * model Origin {
+ *   country: string;
+ *   city: string;
+ *   manufacture: string;
+ * }
+ *
+ * @get
+ * op getModel(): Fish;
+ * ```
  */
 extern dec usage(target: Model | Enum, value: EnumMember | Union, scope?: valueof string);
 
@@ -201,19 +251,143 @@ enum Access {
 }
 
 /**
- * Set access for operations, models and enums. All models that are only used in operations with access "internal" will be implicitly set to access "internal".
+ * Set explicit access for operations, models and enums.
+ * When setting access for models,
+ * the access info wll not be propagated to models' properties, base models or sub models.
+ * When setting access for an operation,
+ * it will influence the access info for models/enums that are used by this operation.
+ * Models/enums that are used in any operations with `@access(Access.public)` will be implicitly set to access "public"
+ * Models/enums that are only used in operations with `@access(Access.internal)` will be implicitly set to access "internal".
+ * This influence will be propagated to models' properties, parent models, discriminated sub models.
+ * But this influence will be override by `@usage` decorator on models/enums directly.
+ * If an operation/model/enum has no `@access` decorator and is not influenced by any operation with `@access` decorator,
+ * the access result is undefined.
  * @param value The access info you want to set for this model or operation.
  * @param scope The language scope you want this decorator to apply to. If not specified, will apply to all language emitters
  *
- * @example
+ * @example Set access
  * ```typespec
+ * // Access.internal
  * @access(Access.internal)
  * model ModelToHide {
  *   prop: valueof string
  * }
+ * // Access.internal
  * @access(Access.internal)
  * op test: void;
  * ```
+ * @example Access propagation
+ * ```typespec
+ * // Access.internal
+ * @discriminator("kind")
+ * model Fish {
+ *   age: int32;
+ * }
+ *
+ * // Access.internal
+ * @discriminator("sharktype")
+ * model Shark extends Fish {
+ *   kind: "shark";
+ *   origin: Origin;
+ * }
+ *
+ * // Access.internal
+ * model Salmon extends Fish {
+ *   kind: "salmon";
+ * }
+ *
+ * // Access.internal
+ * model SawShark extends Shark {
+ *   sharktype: "saw";
+ * }
+ *
+ * // Access.internal
+ * model Origin {
+ *   country: string;
+ *   city: string;
+ *   manufacture: string;
+ * }
+ *
+ * // Access.internal
+ * @get
+ * @access(Access.internal)
+ * op getModel(): Fish;
+ * ```
+ * @example Access influence from operation
+ * ```typespec
+ * // Access.internal
+ * model Test1 {
+ * }
+ *
+ * // Access.internal
+ * @access(Access.internal)
+ * @route("/func1")
+ * op func1(
+ *   @body body: Test1
+ * ): void;
+ *
+ * // undefined
+ * model Test2 {
+ * }
+ *
+ * // undefined
+ * @route("/func2")
+ * op func2(
+ *   @body body: Test2
+ * ): void;
+ *
+ * // Access.public
+ * model Test3 {
+ * }
+ *
+ * // Access.public
+ * @access(Access.public)
+ * @route("/func3")
+ * op func3(
+ *   @body body: Test3
+ * ): void;
+ *
+ * // undefined
+ * model Test4 {
+ * }
+ *
+ * // Access.internal
+ * @access(Access.internal)
+ * @route("/func4")
+ * op func4(
+ *   @body body: Test4
+ * ): void;
+ *
+ * // undefined
+ * @route("/func5")
+ * op func5(
+ *   @body body: Test4
+ * ): void;
+ *
+ * // Access.public
+ * model Test5 {
+ * }
+ *
+ * // Access.internal
+ * @access(Access.internal)
+ * @route("/func6")
+ * op func6(
+ *   @body body: Test5
+ * ): void;
+ *
+ * // undefined
+ * @route("/func7")
+ * op func7(
+ *   @body body: Test5
+ * ): void;
+ *
+ * // Access.public
+ * @access(Access.public)
+ * @route("/func8")
+ * op func8(
+ *   @body body: Test5
+ * ): void;
+ * ```
  */
 extern dec access(target: Model | Operation | Enum, value: EnumMember, scope?: valueof string);