chore: token count tool

package.json

@@ -22,7 +22,8 @@
     "test:update-snapshots": "npm run build && node scripts/test.mjs --test-update-snapshots",
     "prepare": "node --experimental-strip-types scripts/prepare.ts",
     "verify-server-json-version": "node --experimental-strip-types scripts/verify-server-json-version.ts",
-    "eval": "npm run build && node --experimental-strip-types scripts/eval_gemini.ts"
+    "eval": "npm run build && node --experimental-strip-types scripts/eval_gemini.ts",
+    "count-tokens": "node --experimental-strip-types scripts/count_tokens.ts"
   },
   "files": [
     "build/src",

scripts/count_tokens.ts

@@ -0,0 +1,33 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {parseArgs} from 'node:util';
+
+import {GoogleGenAI} from '@google/genai';
+
+const ai = new GoogleGenAI({apiKey: process.env.GEMINI_API_KEY});
+
+const {values, positionals} = parseArgs({
+  options: {
+    model: {
+      type: 'string',
+      default: 'gemini-2.5-flash',
+    },
+  },
+  allowPositionals: true,
+});
+
+if (!positionals[0]) {
+  console.error('Usage: npm run count-tokens -- -- <text>');
+  process.exit(1);
+}
+
+const response = await ai.models.countTokens({
+  model: values.model,
+  contents: positionals[0],
+});
+console.log(`Input: ${positionals[0]}`);
+console.log(`Tokens: ${response.totalTokens}`);