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

Annotations declare readOnlyHint=true, so safety is covered. The description adds no behavioral context beyond the annotation, such as aggregation method, timezone handling, or data scope. It does not contradict 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?

Single sentence, front-loaded, no wasted words. It is efficient, though its extreme brevity leaves no room for structural aids like usage cues.

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?

For a simple read-only tool with fully documented params and readOnly annotation, the description is adequate but incomplete. It doesn't explain return values (no output schema) or distinguish itself from similar siblings like get_spending_summary and compare_periods.

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 coverage is 100% with all three parameters documented, so baseline is 3. The description's parenthetical (daily, weekly, monthly) loosely maps to the period enum but adds little beyond the schema's 'day/week/month' values and date format descriptions.

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 'Get' and resource 'spending trends over time', with granularity options. It clearly identifies the tool's function but does not differentiate from siblings like get_spending_summary or compare_periods.

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 guidance or alternative selection criteria are provided. The description merely states what the tool does, leaving the agent to infer when trends are preferable to summaries or period comparisons.

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