For simple matching scorers, only include explanation if it differs f…

…rom answer

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Add optional `content` parameter to `ModelOutput.for_tool_call()`.
 - Display total samples in Inspect View
 - Prune `sample_reductions` when returning eval logs with `header_only=True`.
+- For simple matching scorers, only include explanation if it differs from answer.
 
 ## v0.3.39 (3 October 2024)
 

src/inspect_ai/scorer/_common.py

@@ -20,13 +20,19 @@ async def score(state: TaskState, target: Target) -> Score:
         for value in target:
             answer, matched = match(state.output.completion, value)
             if matched:
+                explanation = (
+                    state.output.completion
+                    if state.output.completion != answer
+                    else None
+                )
                 return Score(
                     value=CORRECT, answer=answer, explanation=state.output.completion
                 )
 
-        return Score(
-            value=INCORRECT, answer=answer, explanation=state.output.completion
+        explanation = (
+            state.output.completion if state.output.completion != answer else None
         )
+        return Score(value=INCORRECT, answer=answer, explanation=explanation)
 
     return score