Don't force-include the email toolset on every "tell me" query (#1707) (#1735)

The agent tool-RAG force-includes a keyword hint's tools whenever any of its
keywords appears in the query (word-boundary match). The email-intent hint listed
"tell", which matches a huge fraction of requests — e.g. "visit <url> and tell
me the title" — so the whole email toolset was force-included and crowded out the
relevant tools. The model then saw a prompt dominated by email tools and reported
it had no web search / could not visit the URL.

Remove "tell" from the email keyword set. Genuine email intent still fires on
email/mail/gmail/inbox/unread/message/send/reply.

Test drives get_tools_for_query directly with retrieval stubbed (the keyword
hints are deterministic, no embeddings needed): a "...tell me..." web query no
longer pulls in email tools, a real email request still does.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/tool_index.py

@@ -293,7 +293,11 @@ class ToolIndex:
 
     # Keyword hints: if the query mentions these words, force-include the tools.
     _KEYWORD_HINTS = {
-        frozenset({"email", "mail", "gmail", "googlemail", "message", "send", "reply", "inbox", "unread", "tell"}):
+        # NOTE: "tell" was removed from this set. It fired on any "tell me ..."
+        # request (e.g. "visit <url> and tell me the title"), force-including the
+        # whole email toolset and crowding out the relevant tools — the model then
+        # believed it had only email tools and refused web/other tasks (#1707).
+        frozenset({"email", "mail", "gmail", "googlemail", "message", "send", "reply", "inbox", "unread"}):
             {"list_email_accounts", "list_emails", "read_email", "send_email", "reply_to_email", "bulk_email", "delete_email", "archive_email", "mark_email_read", "resolve_contact", "ui_control"},
         frozenset({"calendar", "event", "meeting", "schedule", "appointment"}):
             {"manage_calendar"},