diff --git a/packages/server/src/tools/shell.ts b/packages/server/src/tools/shell.ts
index 1a5516ec..72672473 100644
--- a/packages/server/src/tools/shell.ts
+++ b/packages/server/src/tools/shell.ts
@@ -43,9 +43,14 @@ export class ShellTool extends BaseTool<ShellToolParams, ToolResult> {
 
   getDescription(params: ShellToolParams): string {
     let description = `${params.command}`;
-    // append optional [./directory], prepending ./ if missing (assuming relative per validation)
+    // append optional [./directory], prepending ./ if missing and relative
+    // note description is needed even if validation fails due to absolute path
     if (params.directory) {
-      description += ` [${params.directory.startsWith('./') ? '' : './'}${params.directory}]`;
+      let path = params.directory;
+      if (!path.startsWith('./') && !path.startsWith('/') && path !== '.') {
+        path = './' + path;
+      }
+      description += ` [${path}]`;
     }
     // append optional (description), replacing any line breaks with spaces
     // tool description/schema should specify a single line w/o line breaks