ynab_compare_spending_periods

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint, so safety and idempotency are clear. The description adds 'deterministically' which reinforces idempotency, and 'complete spending periods' clarifies scope. No contradictions exist. Additional context like data sources or side effects is not needed given annotations.

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?

The description is a single sentence that conveys all essential information without redundancy. It is front-loaded with the action and outcome, making it easy to scan. Every word adds value.

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?

Given the tool's complexity (5 parameters, nested objects, output schema exists), the description covers the core purpose and outcome. However, it omits details like the necessity of complete historical periods, handling of missing data, or default behavior for budget_id. The presence of an output schema mitigates the need for return value documentation. Overall, it is nearly complete for a comparison tool.

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%, meaning the description does not explain any parameters. While the schema itself is well-defined with required fields and enums (group_by, period_a, period_b), the description should at least mention the grouping options or the purpose of 'include_transfers' to compensate for the lack of parameter documentation. The rubric requires compensation when coverage is low (<50%), and the description fails to provide it.

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 clearly states the tool's function: 'Compare two complete spending periods and calculate total and per-group differences.' It uses a specific verb ('compare') and resource ('spending periods'), and the result type is clearly defined ('differences'). This distinguishes it from sibling tools like 'ynab_analyze_spending' (general analysis) and 'ynab_compare_transactions' (transaction-level comparison).

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 use when needing to compare two complete spending periods across groups. It does not explicitly state when not to use it or mention alternatives, but the tool name and sibling context (e.g., ynab_compare_transactions) provide clear differentiation. The phrase 'deterministically' hints at reproducibility, which is useful.

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