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

No annotations are supplied, so the description carries the full disclosure burden. "Runs the same code the tool page runs" conveys nothing verifiable about safety, read-only status, or return shape, and nothing is said about what a result contains (pass/fail versus raw record strings) or about rate limits.

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?

Three short fragments with no wasted words, and the subject matter is front-loaded. However, the terseness tips into under-specification, and "Runs the same code the tool page runs" is a provenance remark that does not help an agent decide or invoke.

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-parameter, no-annotation, no-output-schema tool, the description should at minimum say what a result looks like and how it differs from the four other email/DNS check siblings. Neither is covered, leaving the agent unable to predict output or choose correctly.

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 single parameter is fully documented in the schema ("Domain name, no scheme"), which sets the baseline at 3. The description adds no meaning beyond that, such as whether a bare apex domain or subdomain is expected.

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?

"SPF, DKIM and DMARC" identifies the resource being inspected but is a bare noun fragment with no verb, so the agent must infer that this validates email authentication records. It is distinguishable from header tools by the record names, but the near-identical siblings check_dkim, check_email, and check_dns make the scope ambiguous.

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?

"Scope: dns" hints that this is a DNS-record lookup rather than a message-header inspection, which is mild routing value. There is no explicit when-to-use or when-not-to-use statement, and the description never addresses why one would pick this over check_dkim or check_email.

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