list_folders, search_mail, and read_mail have clearly distinct purposes, and check_incremental/acknowledge_checkpoint form a recognizable checkpoint pair. Minor overlap risk exists between search_mail and check_incremental since both revolve around UID batches, but the descriptions distinguish snapshot search from incremental replay.

All five tools use a consistent snake_case verb_noun pattern (list_folders, search_mail, read_mail, check_incremental, acknowledge_checkpoint). No mixed conventions or vague verbless names.

Five tools is well-scoped for a read-only mail client: folder listing, search, reading, incremental sync, and checkpoint acknowledgement. Each tool earns its place with no filler.

For a read-only surface, the set covers the full workflow of discovering folders, finding mail, reading it, and tracking incremental progress via checkpoints. Minor gaps like explicit attachment retrieval exist, but read_mail's MIME return largely covers the need.