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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real value beyond them: it is a paid call ('Costs $0.005 USDC per call (x402)'), which an agent must know before invoking, and it discloses that evidence is returned per detected technology.

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?

Two tight sentences, front-loaded with purpose and the detection categories, with the cost disclosure appended where it belongs. The long parenthetical list is informative rather than padding, though it is slightly dense.

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 a single required parameter, no output schema, and annotations covering the read-only/open-world nature, the definition supplies nearly everything needed. Mentioning that 'evidence for each' is returned partially covers the return shape, which is the only remaining gap.

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 schema description coverage is 100% ('URL or domain'), so the schema already carries the semantics. The description adds little beyond confirming the input is a website, which is the expected baseline when the schema does the work.

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+resource ('Tech stack detection: what a website is built with') and enumerates the categories detected (CMS, frameworks, e-commerce, analytics, ads, CDN, hosting, server). This clearly separates it from nearby siblings like seo, domain_audit, and report_domain, which an agent might otherwise confuse it with.

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?

Usage is implied by the purpose (call it when you need to know a site's underlying technologies), but the description never says when to prefer it over siblings such as domain_audit, seo, or report_domain, nor any prerequisites. Adequate but leaves routing to inference.

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