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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real value beyond them by disclosing ordering ('oldest first'), the in-progress month marker ('complete false on the month in progress'), and the shape of rankedByNetSales. It does not disclose pagination, units, currency, or timezone handling for month boundaries, which matters for a calendar-month aggregation.

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?

Dense but front-loaded: the resource and window come first, then returned fields, then ordering semantics, then the ranked convenience. The nested parenthetical '(default 12, up to 24)' and comma-spliced clauses make it slightly harder to scan than it needs to be, but no sentence is wasted.

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 carries the whole burden of explaining the return value, and it mostly does: named metrics, sort order, the `complete` flag, and the rankedByNetSales companion array. Missing only edge-case behavior (e.g., months with zero sales, currency/units) for full completeness.

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%, so the single `months` parameter is already fully documented with default and min/max. The description restates 'default 12, up to 24' and adds only a minor nuance that the range includes the current month — 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 resource and granularity ('Shopify sales ladder per calendar month') and enumerates the metrics returned (netSales, grossSales, returns, orders), which distinguishes it from monthly-agnostic siblings like get_sales or get_sales_by. It stops short of naming those siblings explicitly, so an agent comparing against get_sales_breakdown still has to infer.

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 shape of the data — a per-month ladder is for trend/month-over-month work — and the 'best month needs no comparing of your own' line hints at a use case. But there is no explicit when-to-use or when-not-to-use versus compare_sales, get_sales, or get_sales_breakdown.

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