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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds genuinely new behavioral context: the data comes from an existing crawl rather than a live fetch, the call is free, and it is throttled at 100 requests/minute per API key. Data staleness ("last crawl") is a relevant caveat an agent could not infer elsewhere.

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 action and the checked factors, then cost and rate limit in short trailing sentences. "Explains per site whether anything blocks indexing" partly repeats the preceding enumeration, which is the only real slack.

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 single optional-parameter read tool with full schema coverage and no output schema, this covers the action, the checked conditions, the scope default, data provenance, cost, and throttling. Nothing essential to invoking it correctly is missing.

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 coverage is 100% and the single parameter already documents "Restrict to one site (optional)". The description only restates this as "all sites (or one)", adding the useful but minor fact that the default is all sites. No additional semantics such as domain format or validation rules.

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 verb and resource ("Check Google indexability") and enumerates the concrete signals it inspects: noindex tags, robots blocks, sitemap errors, canonical problems, redirect chains, broken internal links. Scope is also explicit (all sites or one). It does not name the sibling it differs from (find_issues, get_site_report), so 5 is not warranted.

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 rather than stated: the enumeration of blocking factors plus "Explains per site whether anything blocks indexing" tells an agent this is a diagnostic visibility audit. However, it never says when to pick this over find_issues, get_site_report, or free_page_check, and gives no preconditions such as needing a completed crawl.

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