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

Annotations already declare this a read-only, idempotent, closed-world operation, so the safety profile is covered. The description still adds substantial behavior beyond that: figures are in cents of the home currency (divide by 100), net is inflow minus outflow, counts include unbooked imported bank transactions as well as booked legs so numbers match the bank, empty months are included, and accounts with no movement are omitted from a month. This is a genuinely informative disclosure. It's not a 5 only because it doesn't say how large a range is tolerated or how missing movement is represented (absent key vs zero).

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?

Front-loaded with purpose and the sibling routing before any detail, and each subsequent clause carries information an agent would otherwise guess wrong (cents, inclusion of unbooked transactions). It is dense dash-and-semicolon prose, though, and the unit/exclusion clauses could be split for faster scanning.

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?

There is no output schema, so the description carries the return contract itself and does so fully: bucket granularity, ordering, empty months, absent accounts, currency and units, and the net definition. Combined with 100% schema coverage on the three required parameters, nothing an agent needs to call this correctly is missing.

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% and the description largely repeats what the schema already says about date_from/date_to being YYYY-MM-DD and inclusive. It does add real meaning about the bucketing convention (one bucket per month, oldest first), but that is output shape rather than parameter meaning, so the baseline 3 is right.

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 verb-and-resource: cash in/out per month per cash account over a date range, and grounds it concretely ('the Banking screen's chart as data'). It explicitly distinguishes itself from the two nearest siblings, naming get_income_statement for profit and get_balance_sheet for balances.

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?

Gives both when-to-use ('how much came in and went out each month', runway, seasonality) and when-not-to-use with named alternatives for profit and balance questions. An agent can route correctly without opening any other schema.

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