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

Annotations already establish readOnly, idempotent, non-destructive and open-world behavior, so the bar is lower. The description adds genuinely non-obvious context: the call costs $0.30 USDC on Base or Solana via an X-PAYMENT header, or requires a prepaid key sent as a Bearer token, and fails outside the free trial. It does not mention rate limits or failure modes beyond the payment gate.

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 purpose and output inventory, then payment mechanics in a short second sentence. The output enumeration is long but each item is a distinct capability the agent needs to judge relevance. No filler or repetition.

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 carries the return-value burden and does so by listing the report sections. Payment and auth paths are both spelled out, and required inputs are clear. Missing only sibling differentiation and any sense of result volume/latency.

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 100%, so all three parameters (gl, domain, keywords) are already documented with examples and the 1-8 keyword range. The description restates the keyword bounds but adds no new semantic detail such as keyword format, matching behavior, or how gl affects results. 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 resource (a competitor report keyed to a domain plus 1-8 keywords) and enumerates the payload: rankings, ads/advertisers, SERP features, share of voice, competitors and their top pages, plus the domain's own top pages. That is far more specific than a name restatement. It stops short of distinguishing itself from the closest sibling, seo_audit, which an agent must infer.

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 input shape (one domain, 1-8 keywords, optional country) and the tool explicitly flags that it is not covered by the free trial, which is a real gating condition. However, there is no when-to-use versus when-not guidance and no named alternative such as seo_audit or web_search for a cheaper, narrower lookup.

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