validate_dmarc_record

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

Annotations already declare readOnly, idempotent, and non-destructive behavior, and the description adds further non-obvious facts: no DNS lookup is performed, the output grades findings by level, and a pasted record cannot unlock p=reject. This is substantive behavioral context beyond the annotations.

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?

The key points are front-loaded: use case first, then what validation returns, then the no-DNS-lookup constraint. The upgrade_record caveat is somewhat long and tangential but carries useful routing information, so it earns its place even if it could be tightened.

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 validation tool, the description covers the trigger, the accepted input form, the output categories, and a notable policy limitation. No output schema exists, but the description tells the agent what to expect and to present any returned record verbatim.

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 schema already describes the single parameter thoroughly, including an example and the distinction between the record value and the _dmarc hostname; schema coverage is 100%. The description only restates 'pass the record string itself', so it adds little additional parameter meaning.

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 opens with a specific use case (pasted DMARC record asked about validity/correctness/safety) and names the concrete outputs: parsed tags, level'd findings, and validity. It also states what the tool does not do ('No DNS lookup'), which distinguishes it from check_record and scan_domain.

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?

It explicitly says to use this when the user pastes a DMARC record string, and it contrasts with upgrade_record by explaining when stronger-policy previews are off-limits (p=reject requires reporting-window evidence). This gives the agent clear routing criteria versus related tools.

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