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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered; the description adds genuinely new behavior — London-only coverage, the empty-list-is-not-evidence caveat, cost ('Free'), and result ordering. It stops short of saying what happens when neither optional parameter is supplied or how far 'near' extends, which are the remaining behavioral unknowns.

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?

Front-loaded with purpose, then coverage caveat, then sibling routing, then input format — a sensible order with little waste. The all-caps coverage sentence is effective emphasis rather than padding, though the title restates part of the opening clause.

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?

An output schema exists, so return values need no explanation, and the description covers geography, cost, ordering and alternatives. The gaps are the radius/limit implied by 'near' and the behavior with zero arguments, both of which matter for a tool where all parameters are optional.

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 the load. It does add the crucial format hint for `location` ('lat,lng') and implies the two inputs are alternatives, but leaves `postcode` format unspecified and does not say which wins if both are passed.

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 ('planning applications near a location') plus the exact fields returned (reference, proposal, type, decision, dates) and the ordering (nearest first). It also names the two nearest siblings it is not — `planning_appeals` and `strategic_sites` — 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 explicit routing rules ('For appeals use `planning_appeals`; for allocations use `strategic_sites`'), the geographic precondition ('UK only', 'COVERAGE IS LONDON'), and the input rule ('Give either `postcode` or `location`'). It even warns how to interpret a negative result outside London, which is the main misuse risk for this tool.

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