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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds meaningful non-schema context: the upstream provider (UK PlanIt public aggregator), cost (free) and auth (no key). It does not mention rate limits, result caps, or coverage gaps in the aggregator, which would have earned a 5.

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 short sentences with the purpose front-loaded, followed by sourcing/cost details and the one hard constraint. No filler or repetition.

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 an output schema present, return values need not be described, and readOnlyHint covers safety; the description supplies source, cost, auth and the radius bound. Remaining gaps are minor — result limits/pagination and whether coordinates are WGS84 — but nothing blocks a correct call.

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 0%, so the description must carry parameter meaning; it does define the radius_km valid range (0.1 to 5.0), which is genuinely useful. lat/lon are self-explanatory as a UK coordinate pair, but the default radius of 1 and units/format expectations for coordinates are left unstated.

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 ("Find planning applications near a UK location") plus the data source and its coverage breadth (over 400 authorities). The resource is plainly distinct from the sibling tools (grid connection, BNG cost/income), so an agent can route without opening a 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?

Gives useful operating context — free, no key required, and a hard radius bound — which tells the agent this is a low-friction lookup. However, it never states when to choose this tool over the siblings or what kinds of queries it does not answer (e.g. it is application records, not policy or constraints). Usage is implied rather than guided.

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