Spending summary

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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely non-obvious semantics: amounts are in BRL, positive values represent outflows, and refunds/card payments/deposits are reported separately as credits — critical for interpreting results correctly.

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?

Three sentences, tightly front-loaded with capability first and the sign/currency convention last. Every sentence carries information, though the opening noun-list fragment is dense without a lead verb.

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 usefully enumerates the returned aggregations, and the sign convention covers the biggest interpretation risk. It omits how many merchants/purchases are returned and what the default date range is when from/to are omitted, both of which remain unknown to the agent.

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 both the filters and their formats (date pattern, bank enum, invoice id example) are already documented in the schema. The description restates the filter set but adds no syntax or default-value detail beyond it, making 3 the correct baseline.

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?

The description names specific outputs (totals, spend by bank and category, top merchants, largest purchases), which is a clear verb+resource statement an agent can act on. It does not, however, differentiate itself from siblings like monthly_totals or compare_months, which cover overlapping analytic ground.

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?

It states the available narrowing dimensions ('Optionally narrow by bank, invoice, date range or category'), which implies when the filters apply, but never says when to choose this tool over monthly_totals, compare_months or search_transactions. Usage is inferable but not routed.

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