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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely useful context — 'Costs 1 credit' and the multi-unit 'starting price' nuance — but says nothing about caching behavior (cache_max_age) or failure modes for an open-world fetch.

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 tight sentences with the resource and payload front-loaded, and the cost note at the end. No wasted verbiage; slightly more could be said about the URL prerequisite, but nothing is redundant.

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 usefully enumerates the returned fields, which is the right call. However, it omits the critical prerequisite (obtaining a rental URL via redfin_search) and leaves two of four parameters unexplained, so an agent is not fully equipped to call it correctly.

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 only 50%: 'url' and 'tld' are documented in the schema, but 'country_code' and 'cache_max_age' are undocumented in both schema and description. The description adds nothing about parameter formats or the caching parameter, so it fails to compensate for the coverage 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?

The description names a specific resource and verb: 'Public details for one Redfin rental' and enumerates the returned fields (price, specs, availability, amenities). The 'for-rent' framing implicitly distinguishes it from redfin_forSale, but no sibling is named explicitly, so an agent must infer the routing.

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?

There is no guidance on when to use this versus redfin_search or redfin_forSale, and no note that the required 'url' must first be obtained from redfin_search. The agent is left to infer that this is a detail-fetch step following a search.

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