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

Annotations already declare the read-only, idempotent, non-destructive, non-open-world profile, yet the description adds material context those annotations cannot convey: which columns are populated (~2% price coverage, empty rental/EPC/per-m2), the meaning of tx_n and tx_value, and the UK-only, free constraints. This is exactly the data-quality disclosure an agent needs before building a downstream offering.

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?

The critical warning 'DENSITY ONLY' is front-loaded and the sentences are short and skimmable. Minor redundancy between the header warning and the body, but no wasted prose.

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 the description needn't restate return shapes, yet it still flags the exact data-availability caveat that matters. The main gap is the undocumented area_id/limit inputs, but UK-only, free, and the density-only constraint round out the picture well.

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% and neither area_id nor limit is explained in the description. The description's clarifications (tx_n, tx_value) describe response fields, not the input parameters, so it does not compensate for the schema gap.

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 resource (hex-binned stock and transaction density for map layers) with a precise scope qualifier (H3 resolution 8). Crucially, it differentiates itself from the price-heatmap use case an agent might otherwise assume, so it is distinguishable from siblings like market_yields or valuation_full.

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?

Explicitly warns 'do not offer a price heatmap from this' and leads with 'DENSITY ONLY', which is strong when-not guidance. It stops short of naming a concrete alternative tool for price data, leaving the agent to infer the substitute from the sibling list.

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