ynab_compare_spending_periods

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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. 'Deterministically' is the only added behavioral claim, and it reinforces rather than extends idempotentHint. Nothing is said about how include_transfers alters the totals, whether periods may overlap, or how a zero/empty baseline period is handled.

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?

A single front-loaded sentence with no filler or redundancy. It is efficient, though the terseness leaves the gaps noted in other dimensions rather than wasting space.

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 5 parameters, nested period objects, 0% schema descriptions, and an output schema that removes the need to explain return values, the description should still document input semantics and period-selection rules. It supplies roughly one clause of usable context, leaving an agent guessing on boundary and filtering behavior before a read-only calculation call.

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 0% across 5 parameters, including two nested objects and an enum, so the description must compensate and largely does not. It only loosely implies period_a/period_b and group_by; it never clarifies date-boundary inclusivity (since_date/until_date), the enum values' meaning, the budget_id default, or what include_transfers=false excludes.

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?

Uses a specific verb and resource ('compare two complete spending periods') and names the two outputs ('total and per-group differences'), which maps to the group_by parameter. It does not differentiate itself from plausible siblings like ynab_analyze_spending or ynab_compare_transactions, so an agent cannot tell from the text alone why it should pick this over those.

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?

No when-to-use or when-not-to-use guidance is given, and no alternatives are named despite two closely related siblings (ynab_analyze_spending, ynab_compare_transactions) existing. The phrase 'complete spending periods' weakly implies you must supply full date ranges rather than partial ones, but that is inference, not guidance.

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