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

Goes far beyond the readOnly/openWorld annotations: discloses no-JS execution, the exact failure modes and their names, the $0.01 USDC-on-Base x402 charge that only applies when ok is true, and the missing-payment response behavior. These are billing and behavior traits an agent cannot get from structured fields.

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?

Dense and free of filler; each sentence carries information (limitations, pricing, return contract, payment fallback). The core purpose arrives third rather than first, though leading with limitations is defensible for this tool.

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?

With no output schema, the description still explains the success contract (fields per the supplied JSON Schema) and the failure contract (ok:false plus error codes), and covers the payment precondition. Nothing needed for a correct invocation is missing.

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 both parameters are already documented, and the description largely restates them ('one public page', 'up to 20 properties'). It adds no syntax or format detail beyond the schema, 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: it returns fields described by a JSON Schema from one public page. The static-HTML-only scope further narrows it, so an agent can tell exactly what it does; the lone sibling (gofetch_pricing) is obviously unrelated.

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?

Explicitly names the situations that fail (JS-rendered sites, bot-protected sites) and the failure signals (ok:false, needs_js, blocked), which is strong when-to-use context. It stops short of routing the agent to a sibling tool or stating when to prefer an alternative.

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