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

Annotations already cover read-only, idempotent, non-destructive, closed-world, so the description earns credit for the extras: the methodology (height to inside leg to seat tube), the fact that results are refined with real listing data, and that children are sized by wheel diameter with the tool stating this in its output. It does not discuss caching or data-freshness limits, so not a 5.

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 core purpose is front-loaded in the opening clause and the example anchors it at the end. The first sentence is long with several stacked clauses, but every clause adds information rather than repeating the title.

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 annotations and an output schema already in place, the description covers purpose, method, and the kids edge case, which is what an agent needs to call it. The notable gap is the optional `category` parameter: nothing says what the tool assumes when only heightCm is supplied.

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 only 50% — heightCm has a range description but the 16-value category enum is undocumented. The description maps both inputs conceptually (height, bike category) and usefully flags that for children the height path is replaced by wheel diameter, but it never explains enum values, what 'other' does, or what happens when category is omitted.

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: a frame-size recommendation derived from rider height and bike category, with the exact chart lineage (height to inside leg to seat tube) and the data source (UK listing data). This clearly separates it from siblings like get_spec_sheet (geometry lookup) and recommend_bike_for_budget (budget-based recommendation).

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 worked example ("I'm 178cm — what road-bike size do I need?") gives an unambiguous usage context, and the children note signals the boundary case where height is not the right input. No explicit when-not guidance or named alternative sibling is provided, so it falls short of a 5.

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