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

With no annotations, the description carries the burden itself: it explicitly declares the operation is read-only and discloses what the analysis surfaces (policy value plus warnings for weak or missing policies). It doesn't mention rate limits, auth requirements, or behavior on malformed domains, so it stops short of a full behavioral picture.

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 sentence with a colon-delimited payload, front-loading the action and the _dmarc TXT target, then the returned content, and closing with the read-only trait. No sentence is wasted.

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 one-parameter read-only lookup with no output schema, the description covers the query target, the meaningful output (policy + warnings), and the safety profile. Only the absence of any note on error/empty-result behavior keeps it from being fully complete.

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?

Schema coverage is 100% and there is exactly one parameter, so the schema already fully documents the `domain` input. The description adds the useful notion that the lookup targets the _dmarc TXT record, but gives no additional syntax or format detail beyond the schema's example.

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 (fetch/analyse) and resource (DMARC record via _dmarc TXT), plus the exact payoff: the policy value and warnings. This distinguishes it cleanly from siblings like spf_check, dkim_lookup, and email_posture without needing to name 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?

There is no when-to-use guidance, no mention of when this tool is preferable to spf_check or email_posture, and no stated prerequisites or limits. The usage context is only loosely implied by the subject matter (email authentication posture).

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