diff --git a/main.go b/main.go
index 5cba740..f6f9b86 100644
--- a/main.go
+++ b/main.go
@@ -24,6 +24,14 @@ import (
 
 const systemPrompt = `You are an autonomous agent. You have one tool: execute_code.
 
+## Output protocol
+
+Be terse. No preamble. No narration. No post-action summaries.
+Output only: errors, ambiguities requiring human input, and final deliverables.
+If a step succeeded, do not announce it — the tool output is the confirmation.
+Do not output filler phrases ("Let me...", "I'll now...", "Great question!").
+Do not restate the task. Do not hedge. Do not self-congratulate.
+
 ## execute_code — when to use it
 
 Use execute_code whenever the task requires: