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

Annotations already establish read-only, closed-world, idempotent behaviour, and the description adds meaningful context on top: the non-payment ranking, the three-result cap, GBP pricing with a checked-date caveat, the published fit_rule resource, and the semantics of an empty result. This is well beyond what the structured annotations convey.

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 definition is front-loaded with the core action and then layers output shape, ranking rule, and empty-result handling, each of which earns its place. The long parenthetical category list is the only mildly bloated element, but it usefully delimits scope.

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 return-value burden and does so well: fit score, reasons, specs, evidence links, and a purchase link are all described, plus empty-result semantics. Given nine parameters and a recommendation engine, an agent still lacks guidance on how optional filters interact with ranking, which keeps it below 5.

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 56%, so about half the parameters are undocumented in the schema. The description partially compensates by enumerating the category space (darts, boards, flights, shafts, cases, mats, lighting, surrounds) and noting GBP currency, but it says nothing about use, level, left_handed, or the region restriction beyond the schema itself.

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 states a specific verb and resource: it recommends up to three darts-equipment items from a curated UK catalogue, and it lists the covered categories. An agent immediately knows this is a fit-ranked discovery tool. It does not, however, differentiate itself from the sibling tools compare and get_item, so it falls short of a 5.

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 rather than stated: it is clearly the entry point for 'I want gear' requests, and the instruction to say the catalogue is empty rather than guess is useful handling guidance. But there is no explicit when-to-use versus compare or get_item, and no prerequisites or exclusions, so this stays at minimum-viable.

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