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

Beyond the readOnly/openWorld annotations, the description discloses pagination bounds (about 25 per page, pages 1–20), that results come from public search pages via a premium residential proxy, and a precise cost model: $0.005 USDC per successful call via x402 with failed calls uncharged. That is exactly the kind of billing, sourcing, and failure-behavior context annotations cannot convey.

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?

Front-loaded with the resource and result fields, then the pagination, sourcing, and pricing facts in a compact block. The field enumeration is dense but scannable; it slightly over-lists given an output schema already exists.

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 present, the return values explain themselves; the description covers the remaining agent-critical concerns—pagination ceiling, source reliability, per-call cost, payment rails, and non-charging on failure. Nothing needed to invoke it 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 description coverage is 100%, so the baseline is 3. The description adds only the note that price is GBP and represented monthly rent for lettings; it does not clarify the area-slug format or pagination limits beyond what the schema already states.

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 states a specific resource and scope: Zoopla UK homes for sale or to rent, searched by area, and enumerates exactly which fields come back. An agent can tell this apart from rightmove_property or openrent_uk_listings by the named source and coverage.

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 'homes for sale or to rent in an area', and the 'type' parameter makes the sale/rent split explicit. However, nothing says when to pick this over the many sibling UK property tools (rightmove_property, openrent_uk_listings, purplebricks_property), and no prerequisites are stated.

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