chore: add Google Sheets credential spec (api_key)

tools/src/aden_tools/credentials/google_sheets.py

@@ -0,0 +1,34 @@
+"""
+Google Sheets credentials.
+
+Contains credentials for Google Sheets spreadsheet access.
+Requires GOOGLE_SHEETS_API_KEY for read-only access to public sheets.
+"""
+
+from .base import CredentialSpec
+
+GOOGLE_SHEETS_CREDENTIALS = {
+    "google_sheets_key": CredentialSpec(
+        env_var="GOOGLE_SHEETS_API_KEY",
+        tools=[
+            "sheets_get_spreadsheet",
+            "sheets_read_range",
+            "sheets_batch_read",
+        ],
+        required=True,
+        startup_required=False,
+        help_url="https://console.cloud.google.com/apis/credentials",
+        description="Google API key for reading public Google Sheets",
+        direct_api_key_supported=True,
+        api_key_instructions="""To set up Google Sheets API access:
+1. Go to https://console.cloud.google.com/apis/credentials
+2. Click 'Create Credentials' > 'API Key'
+3. Enable the Google Sheets API in APIs & Services > Library
+4. Target spreadsheets must be shared as 'Anyone with the link'
+5. Set environment variable:
+   export GOOGLE_SHEETS_API_KEY=your-api-key""",
+        health_check_endpoint="",
+        credential_id="google_sheets_key",
+        credential_key="api_key",
+    ),
+}