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

Annotations already establish a safe read-only, idempotent operation, and the description adds substantive behaviour: parcels with no measured coverage are excluded under a ceiling rather than treated as empty, coverage exists for only ~41% of parcels, scope is UK-only, and each call costs 30 credits. The exclusion semantics are the kind of trap an agent would otherwise misread as a vacancy signal.

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 the core output, then the actionable example, then the correctness caveat, then the cost/geography constraints. Every sentence carries information; only the line breaks are slightly heavier than needed.

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 needn't be described, and annotations cover the safety profile. What remains missing is guidance on the undocumented area_id/limit/min_area_m2 parameters, which matters for a costing, area-scoped query tool.

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 carries the full burden. It explains max_built_coverage meaningfully (a ceiling with exclusion semantics) but says nothing about area_id, limit, or min_area_m2, leaving three of four parameters undocumented anywhere.

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?

Opens with a specific verb-resource framing: land parcels described by size and built coverage, which is more precise than the title. It doesn't name a sibling to differentiate from (e.g. parcel_lookup, area_stock_profile), so an agent must infer the boundary itself.

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 a concrete usage pattern — set max_built_coverage to 0.2 to surface largely undeveloped plots — which tells the agent the intended query shape. It stops short of stating when to prefer this over a related tool or when the tool is a poor fit.

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