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

Annotations already cover the read-only/idempotent/non-destructive profile, and the description adds genuinely non-obvious behavior: gross margin returns null when supplier costs are missing and must be reported as unknown rather than zero, plus the default 30-day window and the 'both or neither, never after today' date constraint.

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?

Well front-loaded: metrics and default period first, then the null-margin caveat, then the date parameters. It is slightly dense with parentheticals and the closing clause is a touch emphatic, but nearly every sentence carries operational weight.

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 no output schema, the description correctly enumerates the returned figures including the change-versus-previous-period dimension, and it flags the one non-obvious return state (null margin). Needed behavioral and parameter context for a two-param read-only tool is fully present.

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%, so the baseline is 3, but the description adds real meaning by stressing the consequence of omitting from/to — the call silently reads the last 30 days, which would be wrong for an operator-specified month. That turns a mechanical schema note into a decision-relevant warning.

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 opens with a specific verb+resource scope — 'headline catalogue figures for the current period' — and enumerates the exact metrics returned (revenue, units, AOV, gross margin, out-of-stock SKUs, period-over-period change). This clearly separates it from per-product siblings such as get_top_products or get_product_trends.

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?

It gives explicit routing guidance ('Use first for any question about how the catalogue as a whole is doing') and a strong when-to-use rule: a named month, week, or date range the operator supplied MUST be sent here. What's missing is naming specific sibling alternatives for the cases this tool does not fit, so it stops short of full 5.

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