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

Beyond the read-only/open-world annotations, the description discloses the key constraints: first results page only, maximum 25 results, data read from embedded JSON because no free public read API exists, and the exact x402 payment model including that failed calls are not charged.

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?

A single dense sentence front-loads the resource, location, and scope, then adds sourcing and payment details without repetition. Every clause carries useful operational information.

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?

Given the simple one-parameter schema, existing output schema, and annotations covering safety, the description supplies everything else an agent needs: geography, source, result-count limit, data extraction method, and payment behavior.

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?

The schema already documents the sole `limit` parameter at 100% coverage, including range and default. The description adds the contextual "up to 25" cap but no further syntax or behavioral detail, so the baseline of 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 states a specific resource (UK homes for sale in London), an explicit source (the public rightmove.co.uk search page), and the returned fields. It is clearly distinguishable from sibling real-estate tools by naming Rightmove and London/UK scope.

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 context is clear: London homes for sale from Rightmove's first results page, up to 25. It does not explicitly name alternatives such as Zoopla or OpenRent or state when not to use it, so it falls short of full when/when-not guidance.

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