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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed-world scope, so safety is covered. The description adds one genuinely useful behavioral fact — the figures are derived only from rows already reviewed/categorized as fees — which tells the agent the output depends on prior categorization work. It says nothing about units, currency, or whether cards with no fees appear.

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?

One short sentence with the resource and scope front-loaded and no filler. It is arguably too terse rather than bloated, which is a completeness issue rather than a conciseness one.

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 output schema, the description must carry the return shape, and it only partially does: it implies a per-card annual figure but not whether the result is a list, what fields each card carries, or how interest is separated from fees. For a read-only aggregation tool this is workable but leaves the agent guessing about the response.

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 100% and the single optional 'year' parameter is fully documented in the schema, including its default. The description's 'for a year' merely echoes that. Baseline 3 applies since the schema does all the work.

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?

States a specific resource and scope: interest and fees, broken out per card, for a given year. An agent can tell it is an aggregation/report tool rather than a transaction lister. It does not, however, distinguish itself from the close sibling purch_card_dues, which an agent would have to disambiguate on its own.

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?

There is no statement of when to use this versus purch_card_dues, purch_spend, purch_year, or purch_purchases. The only guidance-like content ('from the rows reviewed as fees') describes data provenance, not selection criteria. An agent must guess from the name alone.

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