Set the category on one or more accounts. Valid categories: CUSTOMER, PROSPECT, OPEN_OPPORTUNITY, CLOSED_LOST, CHURNED, PARTNER, COMPETITOR, OTHER — exactly one per account, and setting a new one replaces the old. Accounts are identified by internal UUID, not name or CRM id. Returns updated_count plus skipped_account_ids: an account is skipped when the id does not exist in this workspace, so a non-empty skipped list means those ids were wrong, not that the write failed. To attach tags use the Tagging service instead.

Use when: Use when the user asks to classify, label or re-classify accounts — 'mark these as customers', 'move Acme to Prospect'. Resolve account UUIDs first via search_accounts_with_filters or get_accounts_by_ids; never guess them. This writes to the workspace and is visible to every user in it, so confirm the account list with the user before calling when the selection came from an ambiguous search.

Behavior: destructive

workspace_id / user_id are injected from request headers.