diff --git a/CHANGES.md b/CHANGES.md
index 7ab5c50f40a..b3751eaadc0 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -7,6 +7,7 @@
 ##### Fixes :wrench:
 
 - Fixed error when resetting `Cesium3DTileset.modelMatrix` to its initial value. [#12409](https://github.com/CesiumGS/cesium/pull/12409)
+- Fixed the parameter types of the `ClippingPolygon.equals` function, and fixed cases where parameters to `equals` functions had erroneously not been marked as 'optional'. [#12394](https://github.com/CesiumGS/cesium/pull/12394)
 - Fixed type of `ImageryLayer.fromProviderAsync`, to correctly show that the param `options` is optional. [#12400](https://github.com/CesiumGS/cesium/pull/12400)
 
 ### 1.125 - 2025-01-02
diff --git a/packages/engine/Source/Core/Color.js b/packages/engine/Source/Core/Color.js
index 8fd5b033119..5f39d2ddac3 100644
--- a/packages/engine/Source/Core/Color.js
+++ b/packages/engine/Source/Core/Color.js
@@ -536,8 +536,8 @@ Color.clone = function (color, result) {
 /**
  * Returns true if the first Color equals the second color.
  *
- * @param {Color} left The first Color to compare for equality.
- * @param {Color} right The second Color to compare for equality.
+ * @param {Color} [left] The first Color to compare for equality.
+ * @param {Color} [right] The second Color to compare for equality.
  * @returns {boolean} <code>true</code> if the Colors are equal; otherwise, <code>false</code>.
  */
 Color.equals = function (left, right) {
@@ -577,7 +577,7 @@ Color.prototype.clone = function (result) {
 /**
  * Returns true if this Color equals other.
  *
- * @param {Color} other The Color to compare for equality.
+ * @param {Color} [other] The Color to compare for equality.
  * @returns {boolean} <code>true</code> if the Colors are equal; otherwise, <code>false</code>.
  */
 Color.prototype.equals = function (other) {
diff --git a/packages/engine/Source/Core/Credit.js b/packages/engine/Source/Core/Credit.js
index bbbe7984a43..863a64be80d 100644
--- a/packages/engine/Source/Core/Credit.js
+++ b/packages/engine/Source/Core/Credit.js
@@ -115,8 +115,8 @@ Object.defineProperties(Credit.prototype, {
 /**
  * Returns true if the credits are equal
  *
- * @param {Credit} left The first credit
- * @param {Credit} right The second credit
+ * @param {Credit} [left] The first credit
+ * @param {Credit} [right] The second credit
  * @returns {boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
  */
 Credit.equals = function (left, right) {
@@ -132,7 +132,7 @@ Credit.equals = function (left, right) {
 /**
  * Returns true if the credits are equal
  *
- * @param {Credit} credit The credit to compare to.
+ * @param {Credit} [credit] The credit to compare to.
  * @returns {boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
  */
 Credit.prototype.equals = function (credit) {
diff --git a/packages/engine/Source/Core/DistanceDisplayCondition.js b/packages/engine/Source/Core/DistanceDisplayCondition.js
index e00e08aec34..8d57139dc70 100644
--- a/packages/engine/Source/Core/DistanceDisplayCondition.js
+++ b/packages/engine/Source/Core/DistanceDisplayCondition.js
@@ -115,8 +115,8 @@ DistanceDisplayCondition.unpack = function (array, startingIndex, result) {
 /**
  * Determines if two distance display conditions are equal.
  *
- * @param {DistanceDisplayCondition} left A distance display condition.
- * @param {DistanceDisplayCondition} right Another distance display condition.
+ * @param {DistanceDisplayCondition} [left] A distance display condition.
+ * @param {DistanceDisplayCondition} [right] Another distance display condition.
  * @return {boolean} Whether the two distance display conditions are equal.
  */
 DistanceDisplayCondition.equals = function (left, right) {
@@ -163,7 +163,7 @@ DistanceDisplayCondition.prototype.clone = function (result) {
 /**
  * Determines if this distance display condition is equal to another.
  *
- * @param {DistanceDisplayCondition} other Another distance display condition.
+ * @param {DistanceDisplayCondition} [other] Another distance display condition.
  * @return {boolean} Whether this distance display condition is equal to the other.
  */
 DistanceDisplayCondition.prototype.equals = function (other) {
diff --git a/packages/engine/Source/Core/OrientedBoundingBox.js b/packages/engine/Source/Core/OrientedBoundingBox.js
index cf4a6d392b4..64d588b06d9 100644
--- a/packages/engine/Source/Core/OrientedBoundingBox.js
+++ b/packages/engine/Source/Core/OrientedBoundingBox.js
@@ -1236,8 +1236,8 @@ OrientedBoundingBox.prototype.isOccluded = function (occluder) {
  * Compares the provided OrientedBoundingBox componentwise and returns
  * <code>true</code> if they are equal, <code>false</code> otherwise.
  *
- * @param {OrientedBoundingBox} left The first OrientedBoundingBox.
- * @param {OrientedBoundingBox} right The second OrientedBoundingBox.
+ * @param {OrientedBoundingBox} [left] The first OrientedBoundingBox.
+ * @param {OrientedBoundingBox} [right] The second OrientedBoundingBox.
  * @returns {boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
  */
 OrientedBoundingBox.equals = function (left, right) {
diff --git a/packages/engine/Source/Core/Spherical.js b/packages/engine/Source/Core/Spherical.js
index 57dca19407f..e0d84bd387e 100644
--- a/packages/engine/Source/Core/Spherical.js
+++ b/packages/engine/Source/Core/Spherical.js
@@ -107,8 +107,8 @@ Spherical.normalize = function (spherical, result) {
 /**
  * Returns true if the first spherical is equal to the second spherical, false otherwise.
  *
- * @param {Spherical} left The first Spherical to be compared.
- * @param {Spherical} right The second Spherical to be compared.
+ * @param {Spherical} [left] The first Spherical to be compared.
+ * @param {Spherical} [right] The second Spherical to be compared.
  * @returns {boolean} true if the first spherical is equal to the second spherical, false otherwise.
  */
 Spherical.equals = function (left, right) {
@@ -145,7 +145,7 @@ Spherical.equalsEpsilon = function (left, right, epsilon) {
 /**
  * Returns true if this spherical is equal to the provided spherical, false otherwise.
  *
- * @param {Spherical} other The Spherical to be compared.
+ * @param {Spherical} [other] The Spherical to be compared.
  * @returns {boolean} true if this spherical is equal to the provided spherical, false otherwise.
  */
 Spherical.prototype.equals = function (other) {
diff --git a/packages/engine/Source/DataSources/DataSourceClock.js b/packages/engine/Source/DataSources/DataSourceClock.js
index 58d55e2a3f0..8bebb21cc2b 100644
--- a/packages/engine/Source/DataSources/DataSourceClock.js
+++ b/packages/engine/Source/DataSources/DataSourceClock.js
@@ -108,7 +108,7 @@ DataSourceClock.prototype.clone = function (result) {
 /**
  * Returns true if this DataSourceClock is equivalent to the other
  *
- * @param {DataSourceClock} other The other DataSourceClock to compare to.
+ * @param {DataSourceClock} [other] The other DataSourceClock to compare to.
  * @returns {boolean} <code>true</code> if the DataSourceClocks are equal; otherwise, <code>false</code>.
  */
 DataSourceClock.prototype.equals = function (other) {
diff --git a/packages/engine/Source/Scene/Billboard.js b/packages/engine/Source/Scene/Billboard.js
index d0612980096..9834474f59b 100644
--- a/packages/engine/Source/Scene/Billboard.js
+++ b/packages/engine/Source/Scene/Billboard.js
@@ -1562,7 +1562,7 @@ Billboard.getScreenSpaceBoundingBox = function (
  * Determines if this billboard equals another billboard.  Billboards are equal if all their properties
  * are equal.  Billboards in different collections can be equal.
  *
- * @param {Billboard} other The billboard to compare for equality.
+ * @param {Billboard} [other] The billboard to compare for equality.
  * @returns {boolean} <code>true</code> if the billboards are equal; otherwise, <code>false</code>.
  */
 Billboard.prototype.equals = function (other) {
diff --git a/packages/engine/Source/Scene/ClippingPolygon.js b/packages/engine/Source/Scene/ClippingPolygon.js
index 3b1886aa44b..566f6941e84 100644
--- a/packages/engine/Source/Scene/ClippingPolygon.js
+++ b/packages/engine/Source/Scene/ClippingPolygon.js
@@ -117,8 +117,8 @@ ClippingPolygon.clone = function (polygon, result) {
  * Compares the provided ClippingPolygons and returns
  * <code>true</code> if they are equal, <code>false</code> otherwise.
  *
- * @param {Plane} left The first polygon.
- * @param {Plane} right The second polygon.
+ * @param {ClippingPolygon} left The first polygon.
+ * @param {ClippingPolygon} right The second polygon.
  * @returns {boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
  */
 ClippingPolygon.equals = function (left, right) {
diff --git a/packages/engine/Source/Scene/Label.js b/packages/engine/Source/Scene/Label.js
index 61168a5ff2c..19b645ac13e 100644
--- a/packages/engine/Source/Scene/Label.js
+++ b/packages/engine/Source/Scene/Label.js
@@ -1364,7 +1364,7 @@ Label.filterUnsupportedCharacters = function (text) {
  * Determines if this label equals another label.  Labels are equal if all their properties
  * are equal.  Labels in different collections can be equal.
  *
- * @param {Label} other The label to compare for equality.
+ * @param {Label} [other] The label to compare for equality.
  * @returns {boolean} <code>true</code> if the labels are equal; otherwise, <code>false</code>.
  */
 Label.prototype.equals = function (other) {
diff --git a/packages/engine/Source/Scene/PointPrimitive.js b/packages/engine/Source/Scene/PointPrimitive.js
index db93554292c..cafd54eabfe 100644
--- a/packages/engine/Source/Scene/PointPrimitive.js
+++ b/packages/engine/Source/Scene/PointPrimitive.js
@@ -665,7 +665,7 @@ PointPrimitive.getScreenSpaceBoundingBox = function (
  * Determines if this point equals another point.  Points are equal if all their properties
  * are equal.  Points in different collections can be equal.
  *
- * @param {PointPrimitive} other The point to compare for equality.
+ * @param {PointPrimitive} [other] The point to compare for equality.
  * @returns {boolean} <code>true</code> if the points are equal; otherwise, <code>false</code>.
  */
 PointPrimitive.prototype.equals = function (other) {