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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description usefully discloses what the check inspects (policy values, alignment, report destinations), which substitutes for the absent output schema, but adds nothing about auth needs, rate limits, or behavior when no record is found.

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 front-loaded sentence that states the action first and then the specific attributes returned. Every clause carries information; no filler or repetition of the title.

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 read-only lookup with no output schema, the description does the necessary work by enumerating the returned fields (existence, validity, policy, alignment, report destinations). It is nearly complete; only edge-case behavior, such as the response when no DMARC record exists, is left unstated.

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?

Only one parameter exists and schema coverage is 100%, with the schema itself supplying the example ('example.com'). The description adds no syntax, format, or validation detail beyond the schema, so the baseline 3 applies.

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 (check) and resource (a domain's DMARC record) and enumerates what the check covers: existence, validity, policy, alignment, and reporting destination. The resource is inherently distinct from siblings like check_spf and check_dkim, but the description never explicitly differentiates itself from them.

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 phrasing 'Check a domain's DMARC record' implies the usage context (validating email authentication for a domain), but there is no explicit when-to-use guidance, no when-not-to-use, and no routing to alternatives such as check_spf or check_email_domain. Usage is inferable but not stated.

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