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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds genuinely useful behavior beyond that: an explicit 5-20 second latency budget and a concrete picture of the return shape (score/grade per area, top fixes, findings with severity/fix/citation). It does not mention rate limits or failure modes, keeping it short of 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 dense sentences, front-loaded with the verb and scope; the second sentence carries returns and latency. Nothing is wasted, though the opening sentence is long enough that its clauses could be split for faster scanning.

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 burden of describing returns, and it does so reasonably (per-area score/grade, top fixes, findings with severity, fix and citation). Combined with 100% schema coverage on inputs and complete safety annotations, an agent has enough to invoke and interpret it; only pagination/result-size limits are unaddressed.

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%, so domain, detail (with enum) and dkim_selectors are all fully documented in the schema itself, including the 's= value' example. The description adds no syntax or format detail beyond that (and never mentions detail or dkim_selectors), so the baseline 3 is appropriate.

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 ('Run every Domain Health check on one domain at once') and enumerates the covered areas (email authentication, SSL/TLS, security headers, registration, DNSSEC). The 'at once' framing and the enumeration together distinguish it from the four per-area sibling tools without opening any schema.

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?

The description makes the aggregation use case clear ('Run every ... check ... at once'), which implicitly routes the agent here instead of calling check_email_auth, check_ssl, etc. individually. However, it never names those siblings or states a when-not condition (e.g. 'use check_ssl for a single fast SSL check'), so selection still requires inference.

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