diff --git a/src/ol/layer/Base.js b/src/ol/layer/Base.js
index 3d4d903d1d..c04d585552 100644
--- a/src/ol/layer/Base.js
+++ b/src/ol/layer/Base.js
@@ -8,6 +8,11 @@ import {assert} from '../asserts.js';
 import {assign} from '../obj.js';
 import {clamp} from '../math.js';
 
+/**
+ * @typedef {import("../ObjectEventType").Types|'change:extent'|'change:maxResolution'|'change:maxZoom'|
+ *    'change:minResolution'|'change:minZoom'|'change:opacity'|'change:visible'|'change:zIndex'} BaseLayerObjectEventTypes
+ */
+
 /**
  * @typedef {Object} Options
  * @property {string} [className='ol-layer'] A CSS class name to set to the layer element.
@@ -47,6 +52,12 @@ class BaseLayer extends BaseObject {
   constructor(options) {
     super();
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<BaseLayerObjectEventTypes, import("../Object").ObjectEvent>}
+     */
+    this.on;
+
     /**
      * @type {Object<string, *>}
      */
diff --git a/src/ol/layer/BaseTile.js b/src/ol/layer/BaseTile.js
index e7f16080a8..ed0e238e7d 100644
--- a/src/ol/layer/BaseTile.js
+++ b/src/ol/layer/BaseTile.js
@@ -61,6 +61,14 @@ class BaseTileLayer extends Layer {
     delete baseOptions.useInterimTilesOnError;
     super(baseOptions);
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("./Base").BaseLayerObjectEventTypes|
+     *     'change:source'|'change:preload'|'change:useInterimTilesOnError', import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("../render/EventType").LayerRenderEventTypes, import("../render/Event").default>}
+     */
+    this.on;
+
     this.setPreload(options.preload !== undefined ? options.preload : 0);
     this.setUseInterimTilesOnError(
       options.useInterimTilesOnError !== undefined
diff --git a/src/ol/layer/Layer.js b/src/ol/layer/Layer.js
index e4dc254cc3..3b3c4d89dc 100644
--- a/src/ol/layer/Layer.js
+++ b/src/ol/layer/Layer.js
@@ -96,6 +96,14 @@ class Layer extends BaseLayer {
 
     super(baseOptions);
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("./Base").BaseLayerObjectEventTypes|
+     *     'change:source', import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("../render/EventType").LayerRenderEventTypes, import("../render/Event").default>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {?import("../events.js").EventsKey}
diff --git a/src/ol/layer/VectorTile.js b/src/ol/layer/VectorTile.js
index debb7e0767..cbb0827623 100644
--- a/src/ol/layer/VectorTile.js
+++ b/src/ol/layer/VectorTile.js
@@ -95,6 +95,14 @@ class VectorTileLayer extends BaseVectorLayer {
       )
     );
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("./Base").BaseLayerObjectEventTypes|
+     *     'change:source'|'change:preload'|'change:useInterimTilesOnError', import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("../render/EventType").LayerRenderEventTypes, import("../render/Event").default>}
+     */
+    this.on;
+
     if (options.renderMode === VectorTileRenderType.IMAGE) {
       //FIXME deprecated - remove this check in v7.
       //eslint-disable-next-line
diff --git a/src/ol/render/EventType.js b/src/ol/render/EventType.js
index adf099b50e..3cb18dc05c 100644
--- a/src/ol/render/EventType.js
+++ b/src/ol/render/EventType.js
@@ -51,5 +51,5 @@ export default {
  */
 
 /**
- * @typedef {MapRenderEventTypes|'prerender'} RenderEventTypes
+ * @typedef {'postrender'|'prerender'} LayerRenderEventTypes
  */
diff --git a/src/ol/source/Image.js b/src/ol/source/Image.js
index 6ab9754ec6..aa032d1a96 100644
--- a/src/ol/source/Image.js
+++ b/src/ol/source/Image.js
@@ -38,6 +38,10 @@ export const ImageSourceEventType = {
   IMAGELOADERROR: 'imageloaderror',
 };
 
+/**
+ * @typedef {'imageloadend'|'imageloaderror'|'imageloadstart'} ImageSourceEventTypes
+ */
+
 /**
  * @classdesc
  * Events emitted by {@link module:ol/source/Image~ImageSource} instances are instances of this
@@ -89,6 +93,13 @@ class ImageSource extends Source {
       state: options.state,
     });
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("../ObjectEventType").Types, import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<ImageSourceEventTypes, ImageSourceEvent>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {Array<number>}
diff --git a/src/ol/source/Tile.js b/src/ol/source/Tile.js
index 8f53d88002..330c4929e9 100644
--- a/src/ol/source/Tile.js
+++ b/src/ol/source/Tile.js
@@ -52,6 +52,13 @@ class TileSource extends Source {
       wrapX: options.wrapX,
     });
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("../ObjectEventType").Types, import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("./TileEventType").TileSourceEventTypes, TileSourceEvent>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {boolean}
diff --git a/src/ol/source/TileEventType.js b/src/ol/source/TileEventType.js
index 3afb10f9d5..b98d18a555 100644
--- a/src/ol/source/TileEventType.js
+++ b/src/ol/source/TileEventType.js
@@ -28,3 +28,7 @@ export default {
    */
   TILELOADERROR: 'tileloaderror',
 };
+
+/**
+ * @typedef {'tileloadstart'|'tileloadend'|'tileloaderror'} TileSourceEventTypes
+ */
diff --git a/src/ol/source/Vector.js b/src/ol/source/Vector.js
index 433bb05e94..7172ad102a 100644
--- a/src/ol/source/Vector.js
+++ b/src/ol/source/Vector.js
@@ -177,6 +177,13 @@ class VectorSource extends Source {
       wrapX: options.wrapX !== undefined ? options.wrapX : true,
     });
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("../ObjectEventType").Types, import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("./VectorEventType").VectorSourceEventTypes, VectorSourceEvent>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {import("../featureloader.js").FeatureLoader}
diff --git a/src/ol/source/VectorEventType.js b/src/ol/source/VectorEventType.js
index a1d6016ad3..01d119093a 100644
--- a/src/ol/source/VectorEventType.js
+++ b/src/ol/source/VectorEventType.js
@@ -56,3 +56,7 @@ export default {
    */
   FEATURESLOADERROR: 'featuresloaderror',
 };
+
+/**
+ * @typedef {'addfeature'|'clear'|'removefeature'|'featuresloadstart'|'featuresloadend'|'featuresloaderror'} VectorSourceEventTypes
+ */