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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety and idempotency are covered. The description goes beyond them with substantive commercial behavior: 0.01 USDC per completed call, automatic x402 payment if the client supports it, and explicitly no charge on failure. It does not mention rate limits, auth prerequisites, or latency, keeping it out of the 5 range.

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 primary action and its return contents, then the pricing terms, with no filler sentences. The detection enumeration is long but every item is load-bearing scope information. Only minor tightening is possible.

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?

No output schema exists, so the description must convey return contents, and it does so concretely (pixel names with IDs, CMS platform, consent tools). The cost/payment mechanic is also disclosed. A little more on response shape or failure modes would be needed for a 5.

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?

There is a single parameter with 100% schema description coverage ('Public http(s) URL of the page or website'), so the schema already carries the semantics. The description adds nothing about the url argument — no accepted forms, trailing-path behavior, or redirect handling — so the baseline 3 is appropriate.

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?

The description uses a specific verb ('Check') and resource (a website's ad pixels/analytics), then enumerates exactly what is detected: Meta Pixel, Google Ads, TikTok, GA4, tag managers, consent tools, CMS platform, booking/chat tools. That is far more precise than a tautology. It does not, however, differentiate itself from the nearby audit_landing_page or sample_audit siblings, so it stops short of a 5.

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 scope list — an agent can infer it should call this when it needs pixel/tag detection for a given URL. But there is no explicit when-to-use, no when-not-to-use, and no mention of how this differs from audit_landing_page or preview_landing_page, which appear to overlap topically.

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