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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context — AUTHORITATIVE sourcing from publishing local authorities via planning.data.gov.uk — though it says nothing about result format or pagination beyond what the schema carries.

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 is front-loaded in the first clause, followed by use cases, parameter behavior, provenance and an example. Every sentence earns its place, though the superlative 'the single most useful call' is mild marketing padding.

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?

For a 5-parameter, read-only spatial query with no output schema, the description covers what is returned, layer restriction, source authority and an example call. Only return-format and pagination details are left to the schema, which is acceptable.

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. The description adds real semantic value by clarifying the dataset parameter's default behavior (omitting it returns every layer at once), which the schema's 'restrict to one layer' wording does not fully convey.

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 ('Return every UK planning designation whose boundary covers one latitude/longitude') and enumerates the concrete questions it answers (conservation area, green belt, flood zone, article 4, local planning authority). The point-in-polygon spatial nature makes it clearly distinct from the sibling search/entity tools even though they are not named.

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?

Gives clear usage context ('site or property due diligence') and explains the key choice — pass a dataset to restrict to one layer or omit it to get every layer at once. It stops short of naming alternative siblings or stating when not to use it, so it is strong but not exhaustive.

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