diff --git a/prompt_templates/mistral.txt b/prompt_templates/mistral.txt
index 21a2fac..f78bed7 100644
--- a/prompt_templates/mistral.txt
+++ b/prompt_templates/mistral.txt
@@ -4,5 +4,9 @@ Email:
 {{email}}
 
 Criterion: {{query}}
-Remember to ONLY return the JSON object described in the system instructions.
+Remember, return ONLY a JSON object on a single line of the form:
+{"match": true} - if the email satisfies the criterion
+{"match": false} - otherwise
+
+Do not add any other keys, text, or formatting.
 [/INST]
diff --git a/prompt_templates/openai.txt b/prompt_templates/openai.txt
index b6b142e..bf7cea1 100644
--- a/prompt_templates/openai.txt
+++ b/prompt_templates/openai.txt
@@ -6,5 +6,9 @@
 {{email}}
 ```
 Classification Criterion: {{query}}
-Remember to ONLY return the JSON object described in the system instructions.<|im_end|>
+Remember, return ONLY a JSON object on a single line of the form:
+{"match": true} - if the email satisfies the criterion
+{"match": false} - otherwise
+
+Do not add any other keys, text, or formatting.<|im_end|>
 <|im_start|>assistant
diff --git a/prompt_templates/qwen.txt b/prompt_templates/qwen.txt
index 4a23068..0c25472 100644
--- a/prompt_templates/qwen.txt
+++ b/prompt_templates/qwen.txt
@@ -6,6 +6,10 @@ Email:
 {{email}}
 
 Criterion: {{query}}
-Remember to ONLY return the JSON object described in the system instructions.
+Remember, return ONLY a JSON object on a single line of the form:
+{"match": true} - if the email satisfies the criterion
+{"match": false} - otherwise
+
+Do not add any other keys, text, or formatting.
 <|im_end|>
 <|im_start|>assistant