diff --git a/schemas/materials/id.schema.yaml b/schemas/materials/id.schema.yaml
index 98468e97c..7cd4efe8b 100644
--- a/schemas/materials/id.schema.yaml
+++ b/schemas/materials/id.schema.yaml
@@ -2,12 +2,19 @@ $schema: "https://json-schema.org/draft/2020-12/schema"
 $id: "schema:ethdebug/format/materials/id"
 
 title: ethdebug/format/materials/id
-description: An opaque external ID (likely generated by compiler)
+description: |
+  An opaque identifier for a compilation resource (such as a source
+  file or a compilation itself), typically generated by the compiler.
+  Values may be numeric or string and **must** be unique within the
+  scope where they appear (e.g., source IDs within a single
+  compilation).
 
 type:
   - number
   - string
 
 examples:
-  - 5
-  - "five"
+  # example: numeric source index
+  - 0
+  # example: content-addressed compilation ID
+  - "__301f3b6d85831638"