diff --git a/server/src/http/mcp.rs b/server/src/http/mcp.rs
index 4a25e9e..590bb59 100644
--- a/server/src/http/mcp.rs
+++ b/server/src/http/mcp.rs
@@ -1610,9 +1610,13 @@ async fn tool_prompt_permission(args: &Value, ctx: &AppContext) -> Result<String
     .map_err(|_| "Permission response channel closed unexpectedly".to_string())?;
 
     if approved {
-        Ok(format!("Permission granted for '{tool_name}'"))
+        Ok(json!({"behavior": "allow"}).to_string())
     } else {
-        Err(format!("User denied permission for '{tool_name}'"))
+        Ok(json!({
+            "behavior": "deny",
+            "message": format!("User denied permission for '{tool_name}'")
+        })
+        .to_string())
     }
 }
 
@@ -3016,4 +3020,55 @@ mod tests {
         assert!(result.is_err());
         assert!(result.unwrap_err().contains("story_id"));
     }
+
+    #[tokio::test]
+    async fn tool_prompt_permission_approved_returns_allow_json() {
+        let tmp = tempfile::tempdir().unwrap();
+        let ctx = test_ctx(tmp.path());
+
+        // Spawn a task that immediately sends approval through the channel.
+        let perm_rx = ctx.perm_rx.clone();
+        tokio::spawn(async move {
+            let mut rx = perm_rx.lock().await;
+            if let Some(forward) = rx.recv().await {
+                let _ = forward.response_tx.send(true);
+            }
+        });
+
+        let result = tool_prompt_permission(
+            &json!({"tool_name": "Bash", "input": {"command": "echo hello"}}),
+            &ctx,
+        )
+        .await
+        .expect("should succeed on approval");
+
+        let parsed: Value = serde_json::from_str(&result).expect("result should be valid JSON");
+        assert_eq!(parsed["behavior"], "allow", "approved must return behavior:allow");
+    }
+
+    #[tokio::test]
+    async fn tool_prompt_permission_denied_returns_deny_json() {
+        let tmp = tempfile::tempdir().unwrap();
+        let ctx = test_ctx(tmp.path());
+
+        // Spawn a task that immediately sends denial through the channel.
+        let perm_rx = ctx.perm_rx.clone();
+        tokio::spawn(async move {
+            let mut rx = perm_rx.lock().await;
+            if let Some(forward) = rx.recv().await {
+                let _ = forward.response_tx.send(false);
+            }
+        });
+
+        let result = tool_prompt_permission(
+            &json!({"tool_name": "Write", "input": {}}),
+            &ctx,
+        )
+        .await
+        .expect("denial must return Ok, not Err");
+
+        let parsed: Value = serde_json::from_str(&result).expect("result should be valid JSON");
+        assert_eq!(parsed["behavior"], "deny", "denied must return behavior:deny");
+        assert!(parsed["message"].is_string(), "deny must include a message");
+    }
 }