diff --git a/explainer/README.md b/explainer/README.md
index 00aaac7e..2c3dce6d 100644
--- a/explainer/README.md
+++ b/explainer/README.md
@@ -131,6 +131,29 @@ There are many channels between the fenced frame tree and the other frames that
 
 This discussion assumes that third-party cookies, like all other third party storage,  are also [disallowed](https://blog.chromium.org/2020/01/building-more-private-web-path-towards.html) or else those would be a communication channel between the fenced frame and the embedding site.
 
+### HTMLFencedFrameElement class
+
+All fenced frame related functions will live in its own class, in the same way that iframe-related funcionality lives in HTMLIFrameElement.
+
+#### Opaque-Ads Can Load API
+
+There are various reasons a fenced frame embedded as an opaque ad could refuse to load in a page. For example, if the page is not in a secure context, or if CSPEE is specified in the embedding frame, the fenced frame will refuse to load. This is a lot for a developer to keep track of.
+
+If the process of getting an ad in the page is complex or expensive, there needs to be a way to ensure that the resulting ad will actually end up in the page before the expensive process begins.
+
+A static API method will be introduced to the HTMLFencedFrameElement class to check this. No fenced frame will be created when calling this API, and it can be invoked before actually attempting to create a fenced frame. The API will return a boolean, true if an opaque-ads fenced frame would be able to load in the caller's context, false if not.
+
+##### Example usage
+
+```
+HTMLFencedFrameElement.canLoadOpaqueURL();
+```
+```
+> true
+```
+
+This is called synchronously, and will look at the execution context of the frame invoking the API.
+
 ## Security considerations
 
 Even though a fenced frame is isolated from its embedding context, it cannot be used as a workaround to the security restrictions that the top-level site wants to enforce on the embedding frames, without the knowledge of the top-level site. The design decisions of fenced frames related to security mechanisms like sandbox, csp, permission policy etc. are based on the following principles: