diff --git a/crates/mcp/src/tests.rs b/crates/mcp/src/tests.rs
index 3051a5ad4..0f3cdd56c 100644
--- a/crates/mcp/src/tests.rs
+++ b/crates/mcp/src/tests.rs
@@ -167,6 +167,16 @@ fn tool_definitions_are_well_formed() {
     }
 }
 
+#[test]
+fn tools_that_write_files_are_not_read_only() {
+    // `render_page` and `screenshot` write a file when given `path`, so they must not advertise `readOnlyHint: true`.
+    for name in ["render_page", "screenshot", "export_png"] {
+        let definition = tool_definitions().into_iter().find(|v| v["name"] == name).unwrap();
+        assert!(definition["inputSchema"]["properties"].get("path").is_some(), "{name} takes a path");
+        assert_eq!(definition["annotations"]["readOnlyHint"], false, "{name} writes files");
+    }
+}
+
 // ---------- layout through the tools ----------
 
 #[test]
diff --git a/crates/mcp/src/tools.rs b/crates/mcp/src/tools.rs
index 8070ab8d3..d1a1ae53a 100644
--- a/crates/mcp/src/tools.rs
+++ b/crates/mcp/src/tools.rs
@@ -233,7 +233,7 @@ pub fn tool_definitions() -> Vec<Value> {
                 }),
                 &[],
             ),
-            true,
+            false,
         ),
         tool(
             "export_png",
@@ -250,7 +250,7 @@ pub fn tool_definitions() -> Vec<Value> {
             "Screenshot",
             &app_only("Capture the whole app window (menus, panels, canvas) and return it as a PNG image. Optionally also keep it at `path`."),
             obj(json!({"path": string("Also write the PNG here")}), &[]),
-            true,
+            false,
         ),
         // ----- input -----
         tool(