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

Goes well past the readOnlyHint/openWorldHint annotations: it discloses the data source (hotpads.com public search pages via residential proxy), the ~40-results-per-page and page 1-20 limits, and a priced x402 payment model ($0.002 USDC per successful call, Base/Solana/Arc, failed calls uncharged). Those are exactly the operational facts an agent needs before spending money.

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 payload description is front-loaded (source, city scope, fields), then filters, then pagination, with pricing last — a sensible ordering. It is a dense run-on sentence that could be broken up, but essentially no filler is present.

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 covering return values and annotations covering safety/open-world character, the description only needs to cover scope, pagination, sourcing, and cost — and it covers all four. Nothing needed to invoke this tool correctly is missing.

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 the baseline is 3, but the description adds meaning beyond the schema: page size (~40 results), the total count returned alongside results, and that rent is USD per month. The city/state/page/type meanings themselves are already fully covered by 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 ('HotPads rental listings for a US city') and enumerates the returned fields (name, type, address, ZIP, bedrooms, rent range, image, link, total). The brand/source name effectively separates it from siblings like realestate_zillow_rentals and realestate_apartments_com, but no sibling is explicitly named as the 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?

Usage is implied by 'for a US city' and the type filter (apartments, houses, condos, townhomes), which tells the agent the scope of a valid call. However, there is no explicit when-to-use guidance, no exclusion conditions, and no routing to the many sibling rental-listing tools, so the agent must infer selection.

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