Lent and borrowed

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds scope behavior that annotations cannot express: results are limited to open loans, overdue entries are flagged, and each record carries a loanId. It stops short of describing ordering or completeness guarantees, so it is strong but not exhaustive.

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?

Content is front-loaded: the resource and its contents come first, then the usage examples and routing hint, then the scope caveat. The opening sentence is somewhat run-on with stacked parentheticals, but every clause (who has it, since when, due date, loanId) carries real information.

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?

With no input parameters and no output schema, the description carries the full burden and does so: it describes what fields each record contains, that only open loans appear, and where returned loans can be found. An agent has everything needed to call it and interpret the result.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and no way for it to under-specify inputs; the baseline applies.

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 names a concrete resource (things lent out and things borrowed), its scope (only open loans, overdue marked), and a distinguishing payload (each with its loanId). It is clearly separable from siblings like item_history and loan_returned, which the text explicitly references.

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?

It gives concrete example questions ("who has the ladder?", "what have I lent out?") plus an explicit routing rule: use this to obtain the loanId needed by loan_returned. It also states an exclusion — returned loans live in each item's item_history — so the agent knows when not to use it.

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