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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description goes beyond them with genuinely non-obvious operational facts: data is scraped from royallepage.ca through a residential proxy, pagination yields about 40 results per page, and each successful call costs $0.01 USDC via x402 (Base, Solana or Arc) with failed calls uncharged. That billing and sourcing context is exactly what annotations cannot express.

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 is front-loaded in the first clause and the field enumeration is dense but scannable. The trailing sibling pointer and payment sentence are useful rather than filler, though the long comma-separated field list is somewhat repetitive given an output schema 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?

For a read-only scraping tool with an output schema, annotations, and full schema coverage, the description supplies the remaining decision-relevant facts: cost model, payment rails, failure billing, proxy sourcing, and page size. Nothing an agent needs to invoke it correctly appears missing; only rate limits or result-cap behavior are absent.

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 city slug format, province code list, and page range are already fully documented in the input schema. The description only adds that results come 'in a city' and 'about 40 per page', which lightly reinforces the page parameter but adds no new constraints. Baseline 3 is appropriate.

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 (Royal LePage homes for sale in a Canadian city) and enumerates exactly what a record contains: listing id, MLS number, price in CAD, address, property type, beds/baths, coordinates, photo and listing link. It is unambiguous about what you get back, though it does not contrast itself against any near-equivalent real-estate sibling (the only sibling it names serves a different domain).

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 the 'homes for sale in a city' framing and the explicit redirect to gov_canada_open_data for federal open datasets, which prevents a plausible mix-up. However, there is no guidance on required scope (province + city), no stated limits on page depth, and no exclusions or alternatives for other property-data needs.

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