Search the library catalog by title or author (case-insensitive, partial matches allowed).

Use this tool whenever the user wants to find books, browse what's available on a topic, or look up a specific author/title but doesn't already know the ISBN. Return a list of matching book records (title, author, isbn, available_copies), or a plain string message if nothing matches.

Check how many copies of a specific book are available to borrow.

Use this tool when the user (or another tool call) already has an ISBN and wants to know stock levels before attempting to borrow, or just want a quick status check on a book.

Borrow a copy of a book on behalf on a library member.

Use this tool when the user wants to check out / borrow a specific book and you already know the ISBN and the member's ID. This reduces the book's availability count by one and records the borrow in the member's history. If there are no copies left or the ISBN/member_id is invalid, and error is returned as a string rather than raised an exception - check the return value before telling the user the borrow succeeded.

Return a previously borrowed book on behalf of a library member.

Use this tool when the user wants to return / check in a book they have borrowed. This increases the book's available copy count by one and records the return in the member's history. Errors (unknown ISBN or empty member_id) are returned as strings, never raised.