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 useful traits beyond that: a hard cap of 10 listings per call, the exact fields returned, and the data-freshness cadence ('new listings land weekly, Sunday to Tuesday UTC'). That is close to rate-limit context, though it says nothing about authentication behavior for the keyed path.

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, front-loaded with the value proposition and the free-tier caveat, then the return shape, then the narrowing advice. No sentence is filler; the key-needed note earns its place by signaling the upgrade path.

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 correctly enumerates returned fields and the max-result cap, and it explains the main parameter combinations for a 12-parameter tool. It omits any mention of pagination limits or how geo-box coordinates interact with city/state, minor gaps given 0 required parameters.

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 100%, so every parameter (including the geo box corners and bed/rent bounds) is already documented in the schema; baseline is 3. The description reinforces how city/state and rent/bed limits combine but adds no syntax or format detail beyond the schema.

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+resource ('Live US rental listings') and scopes it ('for an area and budget, no key needed'), which separates it from the keyed sibling search_my_feed by implication. It never names the sibling outright, so the agent must infer that search_my_feed is the full-coverage alternative.

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 concrete usage guidance: 'Use a state code and a city for one market; add rent and bedroom limits to narrow it,' and flags that a HousingFeed key is required for complete results. It does not explicitly say when to prefer this over search_my_feed or rent_summary, so the routing decision is left partly to inference.

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