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

Adds substantial context beyond the annotations: ~110 fingerprints, 'server HTML only' (a real limitation given rendered siblings), per-call pricing with 25 free and failed-calls-free, and an explicit note that repeat calls are charged. It also restates the read-only/non-mutating profile in operational terms ('reads or computes only and changes nothing'), consistent with readOnlyHint=true and destructiveHint=false.

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-loaded with the core capability and category list, then limitations, then use cases and pricing. Dense but every clause carries information; the pricing sentence is somewhat packed and could be split for scannability.

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?

For a single-parameter, read-only detection tool with no output schema, it covers what is returned ('each with the evidence that matched'), the data source, the fingerprint library size, and cost behavior. An agent has everything needed to decide and invoke correctly.

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 parameter, and the schema already documents it at 100% coverage ('Website or page URL'). The example (url=https://vercel.com/) reinforces the expected format, which is a modest but real addition over the schema.

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 ('detect') and resource ('technologies behind a website') and enumerates the exact categories returned (CMS, JS framework, analytics, CDN, hosting, backend). This clearly separates it from siblings like url_meta or seo_audit, which do not fingerprint a stack.

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 concrete use cases ('lead research, competitor analysis or sales prospecting') and a worked example URL, which tells the agent when to reach for it. It stops short of naming alternatives or exclusions (e.g., when to prefer extract_rendered for JS-heavy sites), so a 4 rather than a 5.

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