diff --git a/README.md b/README.md
index 82a612c8eb..aa7dee9ff6 100644
--- a/README.md
+++ b/README.md
@@ -1976,7 +1976,7 @@ Equivalent to [Plot.vector](#plotvectordata-options) except that the **shape** d
 
 ## Decorations
 
-Decorations are static marks that do not represent data. Currently this includes only [Plot.frame](#frame), although internally Plot’s axes are implemented as decorations and may in the future be exposed here for more flexible configuration.
+Decorations are marks that do not directly represent data. Currently this includes [Plot.frame](#frame), as well as the [axes](#axis) and [grid](#grid) marks described above.
 
 ### Frame
 
diff --git a/src/marks/frame.d.ts b/src/marks/frame.d.ts
index 7c4dd4056d..fc9492c5e0 100644
--- a/src/marks/frame.d.ts
+++ b/src/marks/frame.d.ts
@@ -1,12 +1,40 @@
 import type {InsetOptions} from "../inset.js";
 import type {MarkOptions, RenderableMark} from "../mark.js";
 
+/** Options for the frame decoration mark. */
 export interface FrameOptions extends MarkOptions, InsetOptions {
+  /**
+   * If null (default), the rectangular outline of the frame is drawn; otherwise
+   * the frame is drawn as a line only on the given side, and the **rx**,
+   * **ry**, **fill**, and **fillOpacity** options are ignored.
+   */
   anchor?: "top" | "right" | "bottom" | "left" | null;
+
+  /**
+   * The rounded corner [*x*-radius][1], either in pixels or as a percentage of
+   * the frame width. If **rx** is not specified, it defaults to **ry** if
+   * present, and otherwise draws square corners.
+   *
+   * [1]: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/rx
+   */
   rx?: number | string;
+
+  /**
+   * The rounded corner [*y*-radius[1], either in pixels or as a percentage of
+   * the frame height. If **ry** is not specified, it defaults to **rx** if
+   * present, and otherwise draws square corners.
+   *
+   * [1]: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/ry
+   */
   ry?: number | string;
 }
 
+/**
+ * Draws a rectangle around the plot’s frame, or if an **anchor** is given, a
+ * line on the given side. Useful for visual separation of facets, or in
+ * conjunction with axes and grids to fill the frame’s background.
+ */
 export function frame(options?: FrameOptions): Frame;
 
+/** The frame decoration mark. */
 export class Frame extends RenderableMark {}