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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, but the description adds real context beyond them: detection comes from a single page load, free results are limited to names and categories, and billing is failure-safe (credits auto-refunded, x402 settles only on success). It also spells out the two auth paths (Bearer yatc_ credits key or x402 USDC). The response structure itself is not described, keeping it below a 5.

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?

The core purpose and its output categories are front-loaded in the first sentence, before pricing. The bracketed hub/payment paragraph is long and partly duplicates what the tier parameter and the x402/credits siblings already convey, which costs some tightness but is not severe.

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 must carry the return-value burden, and it does reasonably well by contrasting free (names + categories) with paid (versions, confidence, evidence, DNS/hosting/email, verified SaaS). An agent knows what it will get at each tier. It still lacks any indication of response encoding or interpretation of the confidence/evidence fields.

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 (url, tier) are already fully documented in the schema, including the bare-domain acceptance and the single enum value. The description restates the tier/payment relationship but adds no format or semantics not already in 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 ("Detects the technologies a website uses") and then enumerates the technology categories covered (CMS, ecommerce, JS framework, server, CDN, analytics, pixels, chat, payments, consent), which is unusually precise. It does not, however, distinguish itself from adjacent siblings such as scan_url, audit_website, or check_domain, so an agent still has to reason about which URL-inspection tool to pick.

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 description gives clear guidance on the free-vs-paid decision (omit tier and pay nothing, or pass tier=detect for $0.003 and richer output), which is genuinely useful for choosing how to invoke it. It gives no guidance on when to use this tool instead of the many URL/domain siblings, so the core when-to-use question is only implied by the enumerated output categories.

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