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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the description only needs to add context. It does: internal transfers are excluded, and results are always labelled with the data-currency date — a meaningful disclosure about output freshness. It stays silent on default window size and ordering ties.

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 dense sentences with no filler: purpose and returned fields first, then the exclusion and the freshness caveat. Slightly telegraphic phrasing ('as at') but nothing superfluous.

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 an output schema present, the description need not explain return values, and the annotations cover safety; the exclusion rule and currency-date note fill the remaining behavioural gap. Only the default lookback window and ranking/ordering semantics are left implicit, which the schema largely covers.

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%, so the schema already documents n, oldest-time and newest-time with defaults and formats. The description adds no syntax or constraint detail beyond restating the period concept, so the baseline 3 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?

States a specific resource (merchants the household spent the most with), a time scope (over a period), and the fields returned (total spent, purchase count, category). This clearly separates it from spending_by_category and find_merchant, though it doesn't explicitly name those siblings.

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?

Usage is implied by 'spent the most with over a period' and the exclusion of internal transfers, but there is no explicit when-to-use-this-vs-alternatives guidance (e.g. versus spending_by_category or find_merchant). The period-default note helps, but it lives in the schema, not the description.

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