check_dns

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

Annotations already declare readOnlyHint and openWorldHint, so safety and external-network behavior are covered structurally. The description usefully adds that verification tokens are also fetched from the home page (an HTTP fetch beyond pure DNS), but it omits what happens for an unregistered/invalid domain, whether failures are returned as errors or empty results, and how long the lookup takes.

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?

A single tightly-packed sentence with no filler, and the highest-value information (which record types) comes first. It loses a point for being a sentence fragment with no verb, which slightly weakens front-loading of the actual action.

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 small two-parameter read-only tool with no output schema, enumerating the returned record types is genuinely the right content since nothing else describes the return shape. However, the undefined include_www parameter and the total absence of usage context leave real gaps for an agent deciding when and how to call it.

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?

With only 50% schema description coverage, the description must compensate and does not: it never explains that domain accepts an sc-domain property form, and include_www (default true) is completely unaddressed even though it likely controls the home-page fetch hinted at. The only implicit connection is 'on the home page', which does not explain the parameter's effect.

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 enumerates the exact data returned (A, AAAA, CNAME, MX, NS, TXT, CAA records plus Google verification tokens) but is a bare noun phrase with no verb, so it never explicitly says it looks these up for a domain. It is distinguishable from siblings like robots_txt_check and check_https, but only by the record-type list rather than by a stated action.

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?

There is no when-to-use guidance at all: nothing says to call this when diagnosing DNS/verification problems, and nothing distinguishes it from check_https, check_redirects, or robots_txt_check, which an agent could plausibly pick for a related diagnostic task. The reader must infer the use case entirely.

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