borrow_book

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

No annotations are provided, so the description carries full behavioral disclosure burden. It explicitly discloses the mutation (reduces availability count), the recording of history, and the error-handling behavior (returns string error rather than throwing exception, and instructs to check return value). This is strong disclosure given zero annotations.

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?

Description is appropriately sized - two paragraphs that front-load the core purpose, then add behavioral context. It's efficient and every sentence adds information. Slightly verbose with 'on behalf on' typo and could be tighter, but no wasted sentences.

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?

Output schema exists so return format needn't be explained. The description covers purpose, prerequisites, side effects, error handling, and distinguishing context. For a 2-param tool with full schema coverage, this is quite complete. Slightly less than perfect due to lack of alias/other ISBN format details.

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 coverage is 100%, so the schema already documents both parameters adequately. The description adds the contextual meaning of ISBN and member_id (that they need to be known beforehand), but the schema descriptions are already clear. Baseline 3 is appropriate when schema fully documents parameters.

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?

Description clearly states it borrows a book for a library member, with specific verb+resource+action. It also notes it reduces availability count and records in member history, distinguishing this from siblings like return_book and check_availability.

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?

Description explicitly states when to use this tool (when user wants to check out/borrow and you already know ISBN and member ID). It differentiates from alternatives by noting the prerequisite of knowing the ID/ISBN in advance, which is useful given sibling tools like search_books exist.

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