diff --git a/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/containerInstance.json b/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/containerInstance.json
index f50953347f13..ccc9d8b60a90 100644
--- a/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/containerInstance.json
+++ b/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/containerInstance.json
@@ -522,6 +522,12 @@
             "in": "query",
             "description": "The number of lines to show from the tail of the container instance log. If not provided, all available logs are shown up to 4mb.",
             "type": "integer"
+          },
+          {
+            "name": "timestamps",
+            "in": "query",
+            "description": "If true, adds a timestamp at the beginning of every line of log output. If not provided, defaults to false.",
+            "type": "boolean"
           }
         ],
         "responses": {
@@ -596,6 +602,53 @@
         }
       }
     },
+    "/subscriptions/{subscriptionId}/resourcegroups/{resourceGroupName}/providers/Microsoft.ContainerInstance/containerGroups/{containerGroupName}/containers/{containerName}/attach": {
+      "post": {
+        "operationId": "Containers_Attach",
+        "x-ms-examples": {
+          "ContainerAttach": {
+            "$ref": "./examples/ContainerAttach.json"
+          }
+        },
+        "summary": "Attach to the output of a specific container instance.",
+        "description": "Attach to the output stream of a specific container instance in a specified resource group and container group.",
+        "parameters": [
+          {
+            "$ref": "#/parameters/SubscriptionIdParameter"
+          },
+          {
+            "$ref": "#/parameters/ApiVersionParameter"
+          },
+          {
+            "$ref": "#/parameters/ResourceGroupNameParameter"
+          },
+          {
+            "$ref": "#/parameters/ContainerGroupNameParameter"
+          },
+          {
+            "name": "containerName",
+            "in": "path",
+            "description": "The name of the container instance.",
+            "required": true,
+            "type": "string"
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "schema": {
+              "$ref": "#/definitions/ContainerAttachResponse"
+            }
+          },
+          "default": {
+            "description": "Error response describing why the operation failed.",
+            "schema": {
+              "$ref": "#/definitions/CloudError"
+            }
+          }
+        }
+      }
+    },
     "/subscriptions/{subscriptionId}/providers/Microsoft.ContainerInstance/locations/{location}/cachedImages": {
       "get": {
         "operationId": "Location_ListCachedImages",
@@ -1089,6 +1142,10 @@
             "name": "Scheme",
             "modelAsString": true
           }
+        },
+        "httpHeaders": {
+          "description": "The HTTP headers.",
+          "$ref": "#/definitions/HttpHeaders"
         }
       },
       "required": [
@@ -1706,6 +1763,34 @@
         }
       }
     },
+    "ContainerAttachResponse": {
+      "description": "The information for the output stream from container attach.",
+      "type": "object",
+      "properties": {
+        "webSocketUri": {
+          "type": "string",
+          "description": "The uri for the output stream from the attach."
+        },
+        "password": {
+          "type": "string",
+          "description": "The password to the output stream from the attach. Send as an Authorization header value when connecting to the websocketUri."
+        }
+      }
+    },
+    "HttpHeaders": {
+      "description": "The HTTP headers.",
+      "type": "object",
+      "properties": {
+        "name": {
+          "type": "string",
+          "description": "The header name."
+        },
+        "value": {
+          "type": "string",
+          "description": "The header value."
+        }
+      }
+    },
     "DnsConfiguration": {
       "description": "DNS configuration for the container group.",
       "type": "object",
diff --git a/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/examples/ContainerAttach.json b/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/examples/ContainerAttach.json
new file mode 100644
index 000000000000..d5766b114cd5
--- /dev/null
+++ b/specification/containerinstance/resource-manager/Microsoft.ContainerInstance/stable/2020-11-01/examples/ContainerAttach.json
@@ -0,0 +1,17 @@
+{
+  "parameters": {
+    "subscriptionId": "subid",
+    "api-version": "2020-11-01",
+    "resourceGroupName": "demo",
+    "containerGroupName": "demo1",
+    "containerName": "container1"
+  },
+  "responses": {
+    "200": {
+      "body": {
+        "webSocketUri": "wss://web-socket-uri",
+        "password": "password"
+      }
+    }
+  }
+}