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

Goes well beyond the readOnlyHint/openWorldHint annotations: it discloses a hard quota (3 free MCP calls per day across all tools), paid pricing ($0.005 USDC or card credits), and the exact in-band payment channel (params._meta["x402/payment"]). It also characterizes the detection methodology (HTML, header or DNS evidence; ~70 signatures), which tells the agent how results are produced and how a metered call should be budgeted.

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?

Compact at three sentences with no filler, but the first thing an agent reads is the billing/quota preamble rather than what the tool does, pushing the purpose behind a long list of priced mechanics. The detection categories are dense but each earns its place by scoping the return.

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, omission of return-shape detail is fine, and the one required param is fully described. What's missing is failure behavior on unknown/unreachable domains and whether low-signature sites return partial evidence, which matters for a metered, open-world lookup.

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?

Only one required parameter and schema description coverage is 100%, so the schema already carries the semantics; the description's implicit acceptance of a bare domain ('company website') is consistent with the schema's 'company domain or URL'. It contributes the meta-parameter detail (params._meta payment key) but nothing additional about the domain format.

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 resource and enumerated scope: 'Website tech stack detection: CMS, e-commerce, frameworks, analytics, marketing, support chat, payments, consent, CDN/hosting and email provider'. It also discloses the evidence basis (HTML, header, DNS) and signature breadth (~70), which lets an agent distinguish this from adjacent siblings such as page_meta or dns without opening their schemas.

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 'When to use' sentence only restates what the tool returns ('see which CMS, analytics, chat and payment tools a website uses'), so it adds a cue but no real routing logic. No when-not conditions and no alternatives named (e.g. page_meta for raw tags, dns for records), even though the sibling list is crowded with overlapping tools.

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