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

Annotations already declare readOnlyHint and openWorldHint, but the description adds substantive traits: results are capped at the newest 11 listings, the data comes from an embedded city-page payload via a residential proxy, and billing is $0.01 USDC per successful call via x402 with failed calls uncharged. That payment/limit behavior is not available from annotations alone.

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-loads the source and scope in the first clause, then the returned fields, then pricing. The field enumeration is long but each item tells the agent what it will get; only slight trimming would be 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?

Covers source mechanism, result cap, cost and billing model, and enumerates returned fields even though an output schema exists. Complete enough for an agent to decide and invoke correctly; only the missing sibling/alternative guidance keeps it below top marks.

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% and both parameters already document city slugs and province codes. The description adds no parameter-level detail (e.g., how province/city combine in the URL path), so the baseline 3 applies.

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: REALTOR.ca (Canada MLS) listings for a city, including the exact scope (total count plus the newest 11). The Canadian MLS scope separates it from sibling real-estate listing tools like zillow, zoocasa or rightmove without needing 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?

The description implies usage ('for a city', sourced from the city page's embedded search data) but never states when to prefer this over sibling Canadian or generic listing tools, nor any exclusions. Usage context is inferable but not explicit.

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