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 non-obvious behavior on top: no API key or cost, and the response includes the count, a purchase price, and a one-step buy link. It does not disclose rate limits or how ambiguous locations are resolved, keeping it short of 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 sentences with no waste: the first front-loads what is counted and how, the second covers the free/no-auth trait, the third covers return values. Every sentence carries information an agent cannot get from the structured fields.

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 no output schema, the description appropriately states the return payload (count, price, buy link), and it covers auth/cost. Parameters and location alternatives are fully documented in a 100%-covered schema. What is missing is edge behavior - e.g. what happens with an unmatched or oversized area - which keeps it at a 4 for an 8-parameter, open-world 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 coverage is 100%, so baseline is 3; the description earns a bump by explaining that 'trade' drives property-signal inference rather than plain address filtering, which gives the enum real semantic weight. Location parameters (zip/city+state/lat+lng) are fully described in the schema and not restated, which is appropriate.

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: count households in a service area matching a contractor's trade, with the distinctive detail that matching is judged from property signals (canopy, slope, lot size, pool) rather than addresses. An agent can tell this is a scoped counting step, but the description never names the siblings preview_market or start_checkout, so differentiation is left to inference.

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?

Usage is only implied: 'Free, no key needed' plus returning 'the price to buy' and 'a link where the user can buy the list' sketches a qualify-then-buy funnel, which hints at when this precedes start_checkout. There is no explicit when-to-use, when-not-to-use, or named alternative, so the agent must reconstruct the workflow.

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