lookup_invoice_registration and lookup_invoice_registrations differ only by a trailing 's', so an agent must read descriptions carefully to avoid selecting the wrong one; the batch variant's 'up to ten' limit is the only real discriminator. The history tool is clearly distinct. Boundaries are workable but the singular/plural pair invites misselection.

All three follow a recognizable verb_noun pattern (lookup_*, get_*_history) with consistent snake_case. The only deviation is the near-identical singular/plural naming of the two lookup tools, which is consistent with convention but makes the pair harder to distinguish than ideal.

Three tools for a narrow, single-purpose domain (Japanese invoice registration lookup) is well-scoped and each tool earns its place. One could argue the batch lookup could be folded into the single lookup, but the count itself is not excessive or thin.

The surface covers single lookup, batch lookup, and historical/status data for one number, but has notable gaps: no reverse lookup by registrant name or entity, no batch history retrieval, and no way to list or search registrations. Agents can handle the core validity check but will dead-end on discovery-style queries.