diff --git a/src/tools/prompts.js b/src/tools/prompts.js
index 77ba75b..738cf3d 100644
--- a/src/tools/prompts.js
+++ b/src/tools/prompts.js
@@ -49,7 +49,7 @@ export const TOOL_DESCRIPTIONS = {
     javascript_execute:
         'Execute JS in an isolated sandbox via inline `code` (assign to `module.exports`) or `appletvfsfile` ' +
         '(.applet.js returning typed CSV per @applet-input-schema, @applet-output-schema, and @applet-description; details in applet.SKILL). ' +
-        'Pre-injected globals: fs/vfs, sharp, ExcelJS, PDFDocument, crypto, and fetch("/path"). No require/import.',
+        'Pre-injected globals: fs (vfs; use only root-relative paths for all file operations, absolute paths will fail), sharp, ExcelJS, PDFDocument, crypto, and fetch("/path"). No require/import.',
 
     find_files:
         'List VFS files (root-relative paths). Set skills=true to list root-level "<slug>.SKILL" files.',