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

The description adds substantial behavioral context beyond the read-only/idempotent annotations: it specifies one block per currency, never sums across currencies, and excludes transfer legs. These calculation and filtering behaviors are not present in the annotations or schema and are valuable for correct interpretation of results.

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 tightly written sentences with no filler. The main purpose is front-loaded, followed by two critical constraints. Every sentence earns its place and the structure makes the key facts easy to scan.

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?

The description is behavior-rich but not fully complete for a tool with 4 parameters and zero schema coverage. It lacks explicit guidance on the currency parameter (optional? filter?) and only hints at group_by by mentioning categories, omitting other valid groupings. Given the output schema exists, return values are covered, but input semantics remain partially underspecified.

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?

With 0% schema description coverage, the description carries the burden of explaining parameters. It partially compensates: 'period' implies from/to are date boundaries, 'one block per currency' hints at currency grouping, and 'per-category breakdown' relates to group_by. However, it does not explain the currency parameter's optionality or filtering role, nor does it mention group_by's other allowed values (parent_category, merchant, account), leaving meaningful gaps.

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 states a specific verb and resource: it returns spent/received totals for a period, with currency and category breakdowns. It distinguishes itself from siblings by highlighting the per-currency block and the exclusion of transfer legs, which sets it apart from tools like spending_trend or budget_status.

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?

The description implies usage context (period summary with category breakdown) but never explicitly states when to use this tool over siblings like spending_trend or search_transactions. It gives no when-not guidance or alternative tool names, so the agent must infer the use case from the described behavior.

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