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

Annotations already declare read-only, idempotent, open-world and non-destructive, so safety is covered. The description adds genuinely non-obvious context: no key needed, data freshness ('listings verified at the source in the last 30 days'), and that shared-home rooms are excluded by default — all beyond what the structured fields say.

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?

Two dense sentences with zero filler: the metric list and geographic scope come first, freshness second, and the required input form last. Every clause carries information an agent needs.

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 the return shape (counts plus median/25th/75th percentiles, overall and per bedroom count) and covers input requirements, coverage, and freshness. Nothing essential for a correct call is missing, and the annotations carry the safety profile.

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 all five parameters are already documented, including beds encoding and the include_rooms default. The description only restates the bedroom dimensions and the state+city/ZIP combination rule, adding no format or syntax 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 and resource ('what rent costs right now'), the exact geography (one US city or ZIP), and enumerates the returned statistics (listing count, median/25th/75th percentile, overall and by bedroom count). An agent can distinguish it from search_rentals_sample without opening either 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?

The description gives input guidance ('Give a state and a city or a ZIP') and notes no API key is required, which implies a drop-in lookup. However, it never says when to use this versus the sibling search_rentals_sample, nor what the caller should do when they lack a city/ZIP — usage is implied rather than routed.

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