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

Annotations already declare readOnly/no-open-world/no-destroy, so safety is covered. The description adds real behavioral context beyond that: both sides exclude internal transfers and unattributable money, net position and savings rate are explicitly estimates with stated error sources, and it promises a data-currency date on every answer.

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-loads the resource and period, then layers caveats. The estimate explanation is somewhat dense and leans on income_and_savings, but each sentence carries distinct information (scope, exclusions, estimation limits, freshness) rather than padding.

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, return values need not be described, and the description covers scope, exclusions, estimation caveats and data freshness. The main gap is the absence of explicit routing guidance versus near-neighbor tools.

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 both parameters (newest-time, oldest-time) are fully documented with defaults and format. The description only gestures at 'in a period' and the full-history case, adding no syntax or meaning beyond the schema, so 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 (income, spending, net position, savings rate) with an explicit granularity (per calendar month in a period). It distinguishes itself from siblings by naming income_and_savings and contrasting the 'money moved' total, so an agent can tell them apart without opening a schema.

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 reader infers this is the monthly-breakdown view while income_and_savings gives a single 'money moved' figure. The reference to the sibling is a pointer to a related metric, not an explicit when-to-use/when-not statement, and no guidance is given on precedent over spending_by_category or income_and_expenditure.

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