diff --git a/src/ol/format/Feature.js b/src/ol/format/Feature.js
index 2c93833cd8..210c800bcf 100644
--- a/src/ol/format/Feature.js
+++ b/src/ol/format/Feature.js
@@ -8,14 +8,14 @@ import {get as getProjection, equivalent as equivalentProjection, transformExten
 
 /**
  * @typedef {Object} ReadOptions
- * @property {module:ol/proj~ProjectionLike} dataProjection Projection of the data we are reading.
+ * @property {module:ol/proj~ProjectionLike} [dataProjection] Projection of the data we are reading.
  * If not provided, the projection will be derived from the data (where possible) or
  * the `dataProjection` of the format is assigned (where set). If the projection
  * can not be derived from the data and if no `dataProjection` is set for a format,
  * the features will not be reprojected.
- * @property {module:ol/extent~Extent} extent Tile extent of the tile being read. This is only used and
+ * @property {module:ol/extent~Extent} [extent] Tile extent of the tile being read. This is only used and
  * required for {@link module:ol/format/MVT}.
- * @property {module:ol/proj~ProjectionLike} featureProjection Projection of the feature geometries
+ * @property {module:ol/proj~ProjectionLike} [featureProjection] Projection of the feature geometries
  * created by the format reader. If not provided, features will be returned in the
  * `dataProjection`.
  */
@@ -23,11 +23,11 @@ import {get as getProjection, equivalent as equivalentProjection, transformExten
 
 /**
  * @typedef {Object} WriteOptions
- * @property {module:ol/proj~ProjectionLike} dataProjection Projection of the data we are writing.
+ * @property {module:ol/proj~ProjectionLike} [dataProjection] Projection of the data we are writing.
  * If not provided, the `dataProjection` of the format is assigned (where set).
  * If no `dataProjection` is set for a format, the features will be returned
  * in the `featureProjection`.
- * @property {module:ol/proj~ProjectionLike} featureProjection Projection of the feature geometries
+ * @property {module:ol/proj~ProjectionLike} [featureProjection] Projection of the feature geometries
  * that will be serialized by the format writer. If not provided, geometries are assumed
  * to be in the `dataProjection` if that is set; in other words, they are not transformed.
  * @property {boolean} [rightHanded] When writing geometries, follow the right-hand