Make the extension API docs point out the minimum version that supports an API call.

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "unprivileged": true,
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
@@ skipping 989 matching lines @@
             "type": "integer",
             "name": "windowId",
             "minimum": 0,
             "optional": true,
             "description": "The target window. Defaults to the <a href='windows.html#current-window'>current window</a>."
           },
           {
             "type": "object",
             "name": "options",
             "optional": true,
-            "description": "Set parameters of image capture, such as the format of the resulting image.  This parameter was added in version 5.0 .  Earlier versions of chrome will throw an exception unless you omit it.",
+            "min_version": "5.0.372.0",
+            "description": "Set parameters of image capture, such as the format of the resulting image.",
             "properties": {
               "format": {
                 "type": "string",
                 "optional": true,
                 "enum": ["jpeg", "png"],
                 "description": "The format of the resulting image.  Default is jpeg."
               },
               "quality": {
-                "type": "integer", 
+                "type": "integer",
                 "name": "quality",
                 "optional": true,
                 "minimum": 0,
                 "maximum": 100,
                 "description": "When format is 'jpeg', controls the quality of the resulting image.  This value is ignored for PNG images.  As quality is decreased, the resulting image will have more visual artifacts, and the number of bytes needed to store it will decrease."
               }
             }
           },
           {
             "type": "function", "name": "callback", "parameters": [
@@ skipping 289 matching lines @@
                 "optional": true
               }
             }
           }
         ]
       },
       {
         "name": "setPopup",
         "type": "function",
         "description": "Sets the html document to be opened as a popup when the user clicks on the page action's icon.",
+        "min_version": "5.0.308.0",
         "parameters": [
           {
             "name": "details",
             "type": "object",
             "properties": {
               "tabId": {"type": "integer", "minimum": 0, "description": "The id of the tab for which you want to modify the page action."},
               "popup": {
                 "type": "string",
                 "description": "The html file to show in a popup.  If set to the empty string (''), no popup is shown."
               }
@@ skipping 69 matching lines @@
                 "optional": true,
                 "description": "Limits the change to when a particular tab is selected. Automatically resets when the tab is closed."
               }
             }
           }
         ]
       },
       {
         "name": "setPopup",
         "type": "function",
+        "min_version": "5.0.316.0",
         "description": "Sets the html document to be opened as a popup when the user clicks on the browser action's icon.",
         "parameters": [
           {
             "name": "details",
             "type": "object",
             "properties": {
               "tabId": {
                 "type": "integer",
                 "optional": true,
                 "minimum": 0,
@@ skipping 1697 matching lines @@
         "parameters": [
           {
             "type": "string",
             "name": "text"
           }
         ]
       }
     ]
   }
 ]