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

Annotations only cover safety (readOnly/openWorld/idempotent); the description adds substantial context the agent cannot get elsewhere: personal-looking addresses are never returned (only counted), up to 3 safety-checked redirects, no JavaScript execution, 422 for JS-only pages, and the exact billing semantics (402 unchallenged, failures post-payment uncharged).

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 paid price and core purpose, then layers extraction scope, behavioral limits, and payment mechanics in a tight sequence. Long but every clause carries distinct, decision-relevant 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?

With an output schema present, return values need no explanation, and the description covers the remaining gaps: pricing, the 402 handshake, redirect limits, JS handling, and the no-charge guarantee on errors. Nothing an agent needs to invoke this correctly 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 description coverage is 100%, so the url and payment parameters are already fully documented in the schema. The description restates the payment envelope behavior but adds no syntax or format detail beyond what the schema provides; 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 concrete verb+resource: 'How to reach the organisation behind a website, read from its own HTML,' then enumerates exactly what it extracts (socials, role emails, tel: phones, contact URLs). This scope is unmistakably distinct from web_read, email_check, or domain_intel, though no sibling is named explicitly.

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?

Gives strong procedural guidance for the two-call x402 flow: omit payment on the first call, read howToPay.payloadTemplate from the 402, send the payload on the second call. It lacks any explicit when-to-use-vs-alternative routing (e.g., vs web_read or email_check), which keeps it short of a 5.

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