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

Annotations already declare readOnlyHint and openWorldHint, but the description adds meaningful context beyond them: roughly 40 listings per page, data fetched from royallepage.ca through a residential proxy, and a per-call charge of $0.01 in USDC through x402, with failed calls free. That billing and sourcing detail is exactly the kind of behavioral context an agent needs before spending money, though rate limits and reliability are not covered.

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 first sentence front-loads the resource and its returned fields, and the second covers sourcing and payment; nothing is wasted. The field enumeration is dense, but it is informative rather than filler, so only minor tightening is possible.

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?

Because an output schema exists, return fields need not be enumerated, and the payment, proxy, and pagination details fill in the gaps that structured fields cannot. What is missing is the maximum page count and any statement of coverage limits, though those are relatively minor for a straightforward listing-fetch tool.

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 would be 3, but the description adds the page-size fact of 'about 40 per page', which lets an agent estimate result volume per page using the schema's page range of 1-20. It does not add format hints for city slugs or province codes 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 starts with a specific verb and resource, namely Royal LePage (Canada) homes for sale in a city, and then enumerates the exact fields returned, including MLS number, price in CAD, address, property type, bedrooms and bathrooms, coordinates, photo, and listing link. An agent can tell this apart from the government and B2B directory siblings without opening the 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?

Usage is only implied through the required province and city scoping; the description never says when to prefer this tool over other real-estate or directory tools, nor names any exclusions or prerequisites. It gives enough context for an agent to call it, but there is no explicit when-to-use guidance.

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