DMARC Record Check

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint, non-destructive), so the bar is lower. The description adds real behavioral context beyond that: it warns on monitor-only or partial deployments and exposes a findings[] array, signaling that a present-but-permissive record is a meaningful result rather than an error. No rate-limit or auth notes, but for this tool the annotations plus warning behavior are sufficient.

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 description is compact and front-loads the core purpose in the first sentence, and the example earns its place. However, the Args bullets largely duplicate the schema descriptions, and the Returns line overlaps with the existing output schema — two sections that repeat structured data rather than adding information.

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 low-complexity, read-only DNS tool with full schema coverage, rich annotations, and an output schema, the description is nearly complete: it states the query target, the parsed fields, the warning behaviors, the return shape, and a usage example. The only minor gap is that it never spells out what happens when no DMARC record exists, though the 'found' field implies 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?

The input schema already documents both parameters fully (coverage 100%), including the domain example and the response_format enum/default. The Args block in the description essentially restates the schema ('domain to check', 'output format') without adding deeper meaning such as expected inputs or edge-case rules, so it adds no real value beyond the structured fields.

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 verb+resource ('Fetch and parse a domain's DMARC record (_dmarc.<domain>)') and enumerates the exact fields it extracts (p=, sp=, rua/ruf, pct, aspf/adkim). This clearly distinguishes it from siblings like spf_check, dkim_check, and the generic dns_lookup without needing to open 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 example ('What is paypal.com's DMARC policy?') gives a concrete trigger condition for the tool, and the warning behavior ('warns on monitor-only or partial deployments') hints at when the tool is useful during an audit. It does not explicitly mention exclusions or call out when a sibling like email_auth_audit or dns_lookup would be the better choice, so it stops one step short of a 5.

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