diff --git a/packages/opencode/src/tool/question.txt b/packages/opencode/src/tool/question.txt
index 03cd496d60a..279b530372a 100644
--- a/packages/opencode/src/tool/question.txt
+++ b/packages/opencode/src/tool/question.txt
@@ -8,3 +8,4 @@ Usage notes:
 - When `custom` is enabled (default), a "Type your own answer" option is added automatically; don't include "Other" or catch-all options
 - Answers are returned as arrays of labels; set `multiple: true` to allow selecting more than one
 - If you recommend a specific option, make that the first option in the list and add "(Recommended)" at the end of the label
+- Header must be 12 characters or less (maxLength: 12)
\ No newline at end of file