Spending trends

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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds the return shape (category name mapped to month-by-month values, oldest first, in currency units), which is useful orientation, but it says nothing about pagination, cost, or freshness beyond the lookback window.

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?

Two sentences, no waste, with the core action front-loaded before the return-format detail. Every sentence earns its place.

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 a full output schema present, the description need not explain return values, and it sensibly stops at a one-line orientation. Nothing critical is missing for correct invocation, though the lack of differentiation from sibling summary tools leaves a small gap.

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%: plan_id and months_count (with default 3 and 1–24 bounds) are fully documented in the schema. The description restates the 'N months' concept but adds no new syntax, format, or constraint information beyond it, so the 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 verb and resource ('Return monthly spending trends per category') with a clear temporal scope ('over the last N months'). It is distinguishable from most siblings, though it never explicitly contrasts itself with the nearby get_monthly_summary or get_budget_vs_actual.

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 implied by the scope statement — this is the per-category trend view over a lookback window — but there is no explicit when-to-use, no exclusions, and no routing to alternatives such as get_monthly_summary. An agent must infer the choice from scope wording alone.

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