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

Annotations already cover read-only, idempotent, open-world and non-destructive traits, and the description adds real context on top: the DNS lookup target, the fallback to the organizational domain when no record exists at the subdomain, and the per-call price of $0.005 USDC via x402 on eip155:8453. It stops short of describing the response shape or behavior on NXDOMAIN/timeout.

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 tight sentences: what it reads, what it parses, and what it flags, with cost appended last. Nothing is repeated from the title and no sentence is filler.

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?

With no output schema, the description accepts the burden and lists the parsed tags and weakness categories, plus payment requirements. It leaves the concrete return structure and failure modes unspecified, which keeps it just below complete for an open-world network tool.

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 0%, so the description must carry the single 'domain' parameter — and it does, explaining the query is against '_dmarc.<domain>' and that a bare subdomain will fall back to the organizational domain. That is meaningfully more than the schema's bare string with maxLength 300.

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 and resource (DMARC record check plus parsed policy) and immediately narrows scope to '_dmarc.<domain>' with organizational-domain fallback. The enumerated tags and weakness list make it unmistakably different from dns_spf or email_security.

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 description implies its use case (auditing a domain's DMARC posture) but never says when to pick it over the sibling tools dns_spf or email_security, nor any prerequisites. Usage is inferable rather than stated.

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