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

Annotations already cover the safety profile (readOnly, idempotent, openWorld), so the description's job is to add context — and it does, disclosing the data provenance ('DUO open data') and the exact metric set returned, including benchmarks against national figures. It does not mention result limits, search radius, or whether a partial postcode widens the search.

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?

Two sentences, front-loaded with the cost signal and the core purpose, followed by the attribute list. The metric enumeration is long but each item is a distinct return field, so it earns its space; no filler or marketing language.

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 carry the return shape, and it does so thoroughly (distance, denomination, pupils, test-level shares, per-track pass rates). Gaps are minor: no indication of how many schools are returned, radius, or ordering.

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% and the schema itself supplies format examples ('3511LX or 3511'). The description repeats 'Dutch postcode' without adding syntax or behavioral detail (e.g., how 4-digit vs 6-digit input changes results), so the 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 verb and resource ('nearest primary and secondary schools to a Dutch postcode') and enumerates the returned attributes, making it immediately distinguishable from the home/vehicle/neighbourhood siblings. An agent can tell what this tool answers without opening the schema.

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: supply a postcode, get nearby schools. The 'Free' prefix signals a no-cost option, which is mildly useful routing context, but there is no explicit when-to-use/when-not guidance or named alternative for school lookups.

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