diff --git a/evals/_schemas/config.schema.json b/evals/_schemas/config.schema.json
index 2040f4fd..7e9eb245 100644
--- a/evals/_schemas/config.schema.json
+++ b/evals/_schemas/config.schema.json
@@ -155,7 +155,7 @@
                 "type": ["number", "null"],
                 "minimum": 0,
                 "maximum": 1,
-                "description": "Sampling temperature to send, or null to send nothing so the model uses its own default. Use null for models that require it: Gemini 3 (Google recommends removing the parameter; below 1.0 risks looping and degraded reasoning), GPT-5 (rejects any value but 1 with a 400), and Claude Opus 5 / Opus 4.8 / Opus 4.7 / Sonnet 5 / Fable 5 (sampling parameters removed, 400). Models that still accept one -- Gemini 2.x, GPT-4.x, Claude 4.6 and below -- should carry an explicit number. Required rather than optional so every step records a deliberate choice; an absent key reads as 'nobody considered it'."
+                "description": "Sampling temperature to send, or null to omit the parameter entirely. Prefer an explicit number: the value an evaluator was validated at should be recorded, not inherited from a model default that can change under us. Use null only for models that reject any non-default value -- Claude Opus 4.7 and later return a 400 -- where omitting is the documented approach. A model recommending its default is not grounds for null; write the number out. Required rather than optional so every step records a deliberate choice; an absent key reads as 'nobody considered it'."
               }
             }
           },