diff --git a/src/vscode-dts/vscode.d.ts b/src/vscode-dts/vscode.d.ts
index 180f9bbcaa119..a0852f1837d2e 100644
--- a/src/vscode-dts/vscode.d.ts
+++ b/src/vscode-dts/vscode.d.ts
@@ -182,14 +182,14 @@ declare module 'vscode' {
 		 * The position will be {@link TextDocument.validatePosition adjusted}.
 		 *
 		 * @param position A position.
-		 * @returns A valid zero-based offset.
+		 * @returns A valid zero-based offset in UTF-16 [code units](https://developer.mozilla.org/en-US/docs/Glossary/Code_unit).
 		 */
 		offsetAt(position: Position): number;
 
 		/**
 		 * Converts a zero-based offset to a position.
 		 *
-		 * @param offset A zero-based offset.
+		 * @param offset A zero-based offset into the document. This offset is in UTF-16 [code units](https://developer.mozilla.org/en-US/docs/Glossary/Code_unit).
 		 * @returns A valid {@link Position}.
 		 */
 		positionAt(offset: number): Position;
@@ -257,6 +257,8 @@ declare module 'vscode' {
 
 		/**
 		 * The zero-based character value.
+		 *
+		 * Character offsets are expressed using UTF-16 [code units](https://developer.mozilla.org/en-US/docs/Glossary/Code_unit).
 		 */
 		readonly character: number;