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

With no annotations provided, the description carries the full behavioral burden and does meaningful work: it discloses querying two independent resolvers (cross-checking behavior), full parsing coverage ('every tag'), the JSON return format, and the query-param invocation mechanism. Minor gaps remain—no error behavior, rate limits, or explicit read-only/side-effect declaration—but the core behavioral traits are clearly revealed.

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 sentences with the core function front-loaded; the purpose, behavior, and invocation are each covered in one tight sentence. The only waste is the 'Operated autonomously by AI (RJH Signal Technologies LLC)' attribution, which adds no selection value for the agent.

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?

Given there is no output schema, no annotations, and an empty input schema, the description is nearly the sole information source and covers input, behavior, and output well—including listing the returned tags since no output schema exists. It lacks edge-case handling (domain with no DMARC record, resolver failure) and cost/rate-limit notes, but for a straightforward read-only DNS lookup the invocation loop is fully specified.

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 is empty, so the baseline is 4 per the zero-parameter rule. The description adds essential caller information by documenting the '?domain=example.com' query parameter, which is absent from the schema, and provides a concrete format example. Note: there is a schema–description mismatch (description requires a domain query param while the schema declares no properties), which could confuse strict schema-validating agents, though the description itself compensates by teaching the correct invocation.

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 states a specific verb-resource pair ('Reads and fully parses a domain's DMARC policy record at _dmarc') and enumerates the exact output tags (p, rua, ruf, pct, sp, adkim, aspf) returned as JSON. It differentiates itself from generic siblings like x402-dmarc-check by specifying 'two independent resolvers' and 'fully parses... every tag', so an agent can tell this tool apart without opening the 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?

Usage context is implied by the precise function description, so an agent can infer when to call it (when a domain's DMARC record needs full tag-level parsing). However, there is no explicit when-to-use/when-not-to-use guidance and no mention of alternatives such as x402-dmarc-check, rjhst-email-auth-rec, or rjhst-mta-sts-audit, despite a large cluster of email-security siblings.

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