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

The description goes far beyond the annotations (readOnlyHint, openWorldHint, idempotentHint, destructiveHint=false) by disclosing robots.txt honoring (`Disallow: /` returns 403 `robots_txt_disallow` and skips the fetch), cache write behavior (`Cache-Control: no-store`/`private` sets `cache_respected=false`), per-target eTLD+1 rate limiting (60 req/min), and the `_untrusted` suffix on target-derived data. These operational details are not in annotations and greatly inform safe usage.

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 description is long but each sentence earns its place: it front-loads the core purpose and output, then packs in usage context, audit rules, behavioral constraints, rate limits, and return fields. The structure is logical and dense without padding, making it an efficient reference for an AI agent.

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?

The tool is complex with many edge cases (robots.txt, caching, rate limits, untrusted data), and the description covers all of them explicitly. Error conditions (502 on DNS/TCP/TLS failure, 403 `robots_txt_disallow`) are enumerated, and the comprehensive return field list is provided even though an output schema exists. No critical context is missing for safe and correct invocation.

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?

The input schema already provides 100% coverage for the single parameter `domain`, including 'Registrable domain... No scheme, no path, no port. Strictly homepage-only — the bot fetches https://<domain>/ with HTTP fallback.' The description reinforces this but adds no new parameter-specific semantics beyond the schema. Baseline 3 is appropriate given full schema coverage.

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 clearly states the tool performs a 'One-shot SEO audit of a domain's homepage' and produces a 0-100 composite score plus a `missing_signals` list of fixes. This specific verb+resource combination (audit homepage, score, fixes) distinguishes it from sibling tools like `audit_domain`, `domain_report`, or `geo_audit` by emphasizing SEO focus, homepage-only scope, and the scoring mechanism.

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?

Explicit usage guidance is provided: 'Use BEFORE pitching SEO work to a prospect, when triaging a lead's marketing maturity, or as a structured pre-flight before deeper auditing tools (Lighthouse / SEMrush).' It also explicitly states 'Strictly homepage-only — we do NOT crawl the site,' which differentiates it from crawler-based tools and sets clear expectations for when to use this lightweight audit.

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