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

With no annotations, the description carries the full burden and does well: it discloses the x402 payment requirement, the exact price, the failure mode (payment-required error until _meta payment is attached), and that payment only settles on success. It omits auth requirements beyond payment and any rate/error behavior, but the behavioral disclosure is unusually strong for a paid endpoint.

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?

Three sentences, front-loaded with purpose before the payment mechanics, and every clause carries real information (price, required mechanism, fallback, settlement timing). Slightly dense but no waste.

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?

No output schema, but the description signals the return content ('full listing including contact details'), and the payment workflow — the hardest part of invoking this tool — is fully specified. The missing piece is listing_id format/sourcing and how the paid result is delivered.

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 0% for the single listing_id parameter, so the schema adds nothing. The description partially compensates by embedding {listing_id} in the example URL, implying it identifies the listing, but never states the expected format or where the client obtains the id.

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 (Get) and resource (one full listing) and notes the scope includes contact details, which hints at how it differs from its sibling search_listings. It stops short of explicitly contrasting with search_listings or publish_listing, so an agent must infer the single-item vs list distinction.

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?

It explains the payment/invocation conditions thoroughly (x402 required, HTTP fallback), which is genuinely useful invocation guidance, but says nothing about when to choose this tool over search_listings or publish_listing. Usage relative to siblings is only implied.

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