return_book

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of disclosing behavioral traits. It reveals that the tool mutates loan state, calculates overdue fines at a specific rate ($0.50/day), and fails cleanly when no active loan exists. This is useful behavioral context beyond the raw tool name and schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single, dense sentence that front-loads the primary action, states the important side effects, and includes a critical failure condition. There is no redundant wording or filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple two-parameter tool with an output schema, the description covers the action, effects, and an important error condition. It is sufficient for an agent to invoke correctly. It could be slightly stronger by explicitly noting when this tool should be chosen over check_fines or get_loans, but that is not essential given the straightforward operation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema provides no property descriptions (0% coverage), so the description must compensate. It references 'the member and book,' which maps to member_id and book_id, and the parameter names are self-explanatory. However, it does not explicitly explain that these are the identifiers of the borrowing member and the borrowed book, so the compensation is partial.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Returns a borrowed book'), the target ('for a member'), and the main effects ('closing the loan and calculating any overdue fines'). It also distinguishes itself from sibling tools like borrow_book, check_fines, and get_loans by describing the exact operation and failure condition.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The intended use is implied: call this when a borrowed book is being returned. However, it does not explicitly contrast with alternatives such as check_fines or get_loans, nor does it state when not to use it. The failure condition ('Fails if no active loan exists') provides some guidance about prerequisites but not a full usage policy.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.