Inventory of the user's connected accounts and workspaces: Google (Gmail) accounts, Slack workspaces, and Facebook Messenger. Call this to find out WHICH accounts/workspaces are connected and WHAT each one can do — read/search (`readable`), send (`sendable`), and for Google accounts also Calendar (`calendar`), Drive metadata search (`drive`), Drive CONTENT reads (`drive_content` — read_file_content/download_file_content), Gmail label management (`mail_labels`), Gmail drafts (`mail_drafts`), and Contacts (`contacts` — search_contacts, list_contacts, list_other_contacts, list_contact_groups, get_contact_groups). Questions like "which Gmail/Google accounts are connected?" or "which Slack workspaces can I search or send from?" are answered by this tool — don't guess from search results. It is also the source of the labels accepted by the `accounts`/`account` parameters of search_messages / search_messages_raw / send_message and the calendar/drive/gmail/slack/contacts tools, so call it FIRST to learn valid labels and how many Gmail accounts exist before sending. A false capability means the connection predates that scope — 設定 → サービス連携 で再接続 grants it. Returns, per account: account (label), connector, connector_label, `belongs_to` (the classification label this account's work is filed under — derived automatically when the account is connected: the user's existing label for that company if there is one, otherwise a new label named after the Slack workspace or the mail domain — so a company's Slack and mail share one label; 'プライベート' for personal mail; null = unfiled), readable, sendable, and for Google accounts the capability booleans above; plus `belongs_to_options`: every label the user has, each with its accounts (a label may have none) — these names are the only values add_memory `belongs_to` accepts.