diff --git a/src/schema/objects/columns.yaml b/src/schema/objects/columns.yaml
index bde641ea3b..283b0fa59d 100644
--- a/src/schema/objects/columns.yaml
+++ b/src/schema/objects/columns.yaml
@@ -589,7 +589,7 @@ stim_id:
   name: stim_id
   display_name: Stimulus identifier
   description: |
-    Represents a unique identifier for the stimulus presented at the given onset time.
+    Represents a unique identifier for the stimulus presented at the given onset time. The `stim_id` is inclusive of the stimulus file(s), annotations related to the stimulus, and the information about the stimulus present in the `stimuli.tsv` file.
   type: string
 strain:
   name: strain
diff --git a/src/schema/objects/entities.yaml b/src/schema/objects/entities.yaml
index 0f3b9cfb19..cbf0cd1e51 100644
--- a/src/schema/objects/entities.yaml
+++ b/src/schema/objects/entities.yaml
@@ -194,20 +194,12 @@ part:
   name: part
   display_name: Part
   description: |
-    This entity is used to indicate which component of the complex
-    representation of the MRI signal is represented in voxel data.
-    The `part-<label>` entity is associated with the DICOM Tag
-    `0008, 9208`.
-    Allowed label values for this entity are `phase`, `mag`, `real` and `imag`,
-    which are typically used in `part-mag`/`part-phase` or
-    `part-real`/`part-imag` pairs of files.
-
-    Phase images MAY be in radians or in arbitrary units.
-    The sidecar JSON file MUST include the `"Units"` of the `phase` image.
-    The possible options are `"rad"` or `"arbitrary"`.
-
-    When there is only a magnitude image of a given type, the `part` entity MAY be
-    omitted.
+    This entity is used to indicate which component of a complex 
+    representation is being stored. For MRI data, it indicates which component 
+    of the complex signal is represented in voxel data. For stimulus files, it can 
+    be used to distinguish different parts of a single stimulus, such as chapters 
+    in an audiobook or segments of a long movie (for example, `part-1`, `part-2`, 
+    `part-epilog`, `part-chapter1`).
   type: string
   format: label
   enum:
@@ -377,12 +369,13 @@ stimulus:
   name: stim
   display_name: Stimulus
   description: |
-    The `stim-<label>` entity can be used to distinguish different stimulus files or annotations.
-    The label is a unique identifier for the stimulus or annotation.
+    The `stim-<label>` entity can be used to distinguish different stimulus files 
+    or annotations. The label is a unique identifier for the stimulus or annotation.
 
-    This entity represents the `"Stimulus"` metadata field.
-    Therefore, if the `stim-<label>` entity is present in a filename,
-    `"Stimulus"` MUST be defined in the associated metadata.
+    This entity represents the `"Stimulus"` metadata field and requires corresponding 
+    entries in the `stimuli.tsv` file. Therefore, if the `stim-<label>` entity is 
+    present in a filename, `"Stimulus"` MUST be defined in the associated metadata, 
+    and a matching entry MUST exist in the `stimuli.tsv` file.
   type: string
   format: label
 subject:
@@ -455,3 +448,13 @@ tracksys:
     may be longer and more human readable.
   type: string
   format: label
+annotation:
+  name: annot
+  display_name: Annotation
+  description: |
+    The `annot-<label>` entity accommodates multiple annotations for a single 
+    (usually, but not necessarily, time-varying) stimulus id. Similar to `stimuli.tsv`, 
+    there can be one or multiple `annotations.tsv` files with `annotation_id`, providing 
+    a list of the annotations in the directory, or for a specific stimulus respectively.
+  type: string
+  format: label