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

Annotations already declare this a safe, idempotent, closed-world read, so the bar is lower. The description still adds real behavior beyond them: results are ordered by straight-line distance from the postcode centre, each record carries Ofsted outcome, selective status and religious character, and — importantly — the last-distance-offered figure is gated to signed-in pass holders, which an agent must know to interpret partial results.

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?

Purpose and ordering are front-loaded in the first sentence, with the return-shape and gating detail following. It is dense but each clause carries information; the second sentence is long and could be split for readability without losing content.

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 must characterize results, and it does: it names ordering, distance metric, the per-school attributes, and the paywall constraint on the distance figure. It stops short of describing result envelope details (count, paging beyond limit, behavior when nothing is in radius), which is a minor remaining gap.

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 high (86%), so the baseline is 3. The description nevertheless adds meaning: distance is measured as straight-line from the postcode centre (clarifying radius_miles), postcode accepts a district such as SE22, and published_distance_only corresponds to 'whether a last distance offered has been published' — reinforcing what the returned flags mean.

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 ('List schools, nurseries and childcare') plus scope ('near an England postcode') and ordering ('nearest first, by straight-line distance'). This is clearly distinguishable from a name lookup like find_school or a single-record get_school; an agent can route on the geographic-search framing alone.

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: the postcode-accepting scope signals when the tool applies, and radius_miles/published_distance_only hint at narrowing use. However, no sibling is named and no when-not condition (e.g., use find_school for name lookup, get_school for a single known school) is provided, leaving the agent to infer tool selection.

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