diff --git a/plugin/scripts/inject-instructions.mjs b/plugin/scripts/inject-instructions.mjs
index a159190..1539b52 100644
--- a/plugin/scripts/inject-instructions.mjs
+++ b/plugin/scripts/inject-instructions.mjs
@@ -114,6 +114,30 @@ if (forceDisabled) {
   process.exit(0);
 }
 
+// Validate JFROG_URL early to surface misconfigurations before the MCP server
+// attempts to connect and fails with a confusing DNS or double-slash error.
+if (!process.env.JFROG_URL) {
+  const missingUrlWarning = "WARNING: JFROG_URL is not set. The JFrog MCP server will be unreachable — set JFROG_URL to your Artifactory base URL (e.g. https://mycompany.jfrog.io) and restart.";
+  log(missingUrlWarning);
+  process.stdout.write(JSON.stringify({
+    hookSpecificOutput: {
+      hookEventName: "SessionStart",
+      additionalContext: `IMPORTANT: Immediately tell the user: "${missingUrlWarning}"`,
+    },
+  }));
+  process.exit(0);
+} else if (process.env.JFROG_URL.endsWith("/")) {
+  const trailingSlashWarning = "WARNING: JFROG_URL has a trailing slash. This produces a double-slash in the MCP URL and will silently fail — remove the trailing slash and restart.";
+  log(trailingSlashWarning);
+  process.stdout.write(JSON.stringify({
+    hookSpecificOutput: {
+      hookEventName: "SessionStart",
+      additionalContext: `IMPORTANT: Immediately tell the user: "${trailingSlashWarning}"`,
+    },
+  }));
+  process.exit(0);
+}
+
 if (forceEnabled) {
   debug("Force-enable flag is set.");
 } else if (!(await isAgentGuardEnabledViaSettings())) {