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 profile is covered. The description adds genuinely non-obvious behavior: a paid API key is required, the exact auth header format, the price point ($15 per 3 months), and the metric scope ceiling. It stops short of stating rate limits, error behavior, or how results are returned.

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?

The core capability and its metric list are front-loaded in the first sentence, followed by a scope exclusion and then the access requirement. The dense metric enumeration is long but every item earns its place by telling the agent what data comes back; a bulleted structure would read slightly better.

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 two-parameter read-only comparison tool with no output schema, the definition covers scope, metric coverage, competitor limits, exclusions, authentication, and cost — everything an agent needs before invoking it. The only absent piece is return-value shape, which the metric list effectively implies.

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% and both parameters are documented ("Your page", "Competitor pages", minItems 1 / maxItems 3). The description reinforces the 3-competitor cap and the your-page-vs-competitors distinction but adds no new syntax or format guidance (e.g., absolute URL requirements). 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?

The description opens with a specific verb+resource pair ("side-by-side ... signals for your page and up to 3 competitor pages") and then enumerates the exact metrics compared: response time, title/description length, H1, word count, JSON-LD types, llms.txt, blocked AI crawlers, security headers. It explicitly carves out what it does NOT cover ("No backlink or domain-authority metrics"), which separates it from a general SEO sibling.

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 framing (compare your page against competitor pages) and the exclusions clarify when another metric-oriented tool is needed. However, no sibling is named and there is no explicit when-to-use/when-not guidance versus tools like seo_check or security_headers_check, which partially overlap with the on-page and header signals listed here.

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