renew_loan

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

Annotations already declare this is a non-read-only, non-destructive, open-world mutation. The description adds meaningful context beyond that: renewal is only possible from the renewable_on date, and the agent must confirm with the user before acting. It still does not describe the effect of renewal (e.g., due-date extension) or failure conditions like renewal limits.

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 front-loaded sentences with no wasted text. The parenthetical 'its renewable_on date' is slightly ambiguous because renewable_on is not a parameter, but overall the structure is efficient.

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 three-parameter mutation with an output schema, the description covers the essential precondition and confirmation requirement. It leaves out what happens on failure (e.g., renewal limits) and what the renewal actually changes, which would be useful for a mutation tool even with annotations and schema coverage.

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 days, library, and title_id are already fully documented in the schema. The description adds no parameter-specific guidance beyond the timing context, which is appropriate given the schema does the heavy lifting.

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 states a specific verb and resource ('Renew a loan'), which is clearly distinct from siblings such as borrow, return_loan, and place_hold. It adds a timing qualifier ('possible from its renewable_on date'), but does not explicitly contrast itself with any sibling tool.

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 a concrete precondition ('possible from its renewable_on date') and a workflow rule ('Confirm with the user first'), which tells the agent when renewal is allowed and that user confirmation is required. It does not name alternatives or explain what to do when renewal is unavailable.

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