Account totals by month

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

Annotations already establish readOnly, idempotent, non-destructive and open-world behavior, so the bar is lower. The description still adds a genuinely non-obvious behavioral trait: revenue accounts (3xxx+) are sign-flipped so income reads positive, which an agent could not infer from the schema or annotations and which materially affects result interpretation.

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 sentences, front-loaded with the core operation before the examples. The range examples occupy most of the text but each one earns its place by disambiguating the account parameters; nothing is redundant filler.

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 four-required-parameter read tool with no output schema, the definition covers what the tool computes and the sign-flip rule, but says nothing about the shape of the result (per-month series, currency, whether empty months appear) or how the date range interacts with monthly bucketing.

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 0%, so the description must carry the parameter burden, and it does for the two account parameters by mapping number ranges to business meaning (3000–3999 revenue, 7000–7699 personnel, 1930 business account). The date parameters get no explanation, but their ISO pattern and the required from/to pairing are self-evident.

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 operation (monthly net movement) over a specific resource (an account-number range), which clearly distinguishes it from aggregate siblings like income_statement and balance_sheet. The concrete range examples (3000–3999 revenue, 5000–6999 external costs) pin down the domain precisely, though no sibling is named as an explicit alternative.

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 only implied: the account-range examples hint at when this tool applies (per-month account aggregation), but there is no explicit statement of when to use it versus income_statement, balance_sheet, or list_vouchers, and no prerequisites or exclusions are given.

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