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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: the last-distance-offered and catchment/priority-area fields are only present for a signed-in pass holder, and the postcode parameter changes the result shape. It says nothing about behaviour for an unknown or malformed ID, which is the remaining gap.

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?

Three sentences, front-loaded with the resource and ID, then the payload, then the conditional extras and the postcode modifier. Dense but every clause carries information; the '(see get_admission_distances)' cross-reference is compact routing rather than filler.

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-value burden, and it does by listing the data sections, including the auth-gated ones. For a 2-parameter read tool with full annotation coverage this is close to complete; only error/not-found behaviour and response shape granularity are absent.

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%, so the baseline is 3, but the description earns an extra point by telling the agent where school_id comes from (find_school or search_near_postcode) — provenance the schema's 'Catchmently ID, e.g. gias:138342' does not convey. The postcode explanation merely restates the schema's 'straight-line distance' wording, so it adds little.

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?

Names a specific resource and scope ('Details for one school or nursery by Catchmently ID') and enumerates exactly what comes back: register details, latest Ofsted outcome with quoted strengths and areas to improve, exam results, applications and offers. Even without the sibling list an agent could tell this apart from a search or distance tool.

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?

It routes the agent on ID provenance ('from find_school or search_near_postcode') and points to get_admission_distances for the fuller distance data, plus states that supplying a postcode adds a straight-line distance. What's missing is an explicit exclusion, e.g. that this is not for finding a school when you only have a name or postcode.

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