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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety bar is low. The description adds genuinely useful non-schema behavior: the payment protocol (x402), exact price ($0.10 USDC flat on Base or Solana), the required X-PAYMENT header, and trial exclusion. It does not describe latency, failure modes on unpaid calls, or result volume, which keeps it from 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?

Two sentences, front-loaded with what is returned and followed by the payment constraint; every clause carries information with no filler. It is dense but readable, and the pricing detail is appropriately separated from the capability statement.

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 usefully sketches the report contents, and it covers the payment prerequisite that would otherwise cause a failed call. The gap is the undocumented gl parameter and the absence of any note on what a paid-but-invalid request returns, which matters for a metered tool.

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 description coverage is 0%, so the description must carry parameter meaning. It clarifies that keywords is a list of 1-10 terms and that brand may be a brand or domain, but the third parameter, gl, is never mentioned and its meaning (geo/locale) must be guessed from the abbreviation.

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 ('report') and names concrete outputs: SERP rank, AI Overview, answer box, People Also Ask, knowledge graph presence, competitors, and a 0-100 score, explicitly scoped to 1-10 keywords. That makes it clearly distinct from sibling tools like seo_audit or competitor_report, though it never names or contrasts those siblings directly.

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 context is implied (brand-visibility auditing) and two real gating conditions are stated: it is paid via x402 and not included in the free trial. However, there is no explicit guidance on when to choose this over seo_audit or competitor_report, nor any note about repeat calls being unnecessary despite idempotence.

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