borrow_book

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

No annotations are present, so the description carries the full burden. It discloses the mutation side effect (a loan record is created) and, more valuably, both failure modes (no available copies; already-active loan), which spares the agent from a doomed invocation. It stops short of addressing permissions or reversibility, but that is a minor gap given the output schema covers the return value.

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?

Two sentences with zero filler: the action is front-loaded and the second sentence adds high-value failure information. Every word earns its place.

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 low-complexity tool (two required integer params, no nesting, output schema present), the description covers the action, the side effect, and both relevant failure conditions. The missing sibling routing is a minor gap that does not undermine an agent's ability to invoke the tool correctly.

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?

Schema description coverage is 0%, so the description must compensate. It maps member_id to the borrowing member and book_id to the book being borrowed, and the failure conditions add constraints on which values are acceptable (a book with available copies, a member without an active loan). This is useful but stays at role-and-constraint level, offering no source or lookup guidance for the IDs.

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 opens with a specific verb ('Borrows'), a concrete resource ('a book'), a beneficiary ('a member'), and the resulting side effect ('creating a loan record'). The purpose is unmistakable and naturally contrasts with the sibling return_book, so an agent can tell it apart without opening any schema.

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 description implies the usage context — use this when a member wants to borrow a book — but never explicitly states when-not-to-use or names alternatives such as return_book for returning or get_loans for inspecting existing loans. The 'Fails if' clause provides useful preconditions, but explicit routing guidance is absent.

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