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

With no annotations, the description carries the burden and does so reasonably: it discloses the free-tier quota, that MTA-STS policy is checked against the MX hosts (a real DNS-lookup behavior), and that the response includes a reusable snapshot. It stops short of stating read-only/safety posture, error handling for invalid domains, or latency despite multiple DNS lookups.

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?

One dense sentence with no filler, and the cost/limit constraint is front-loaded before the capability list. The long enumeration of output fields is informative rather than padding, given there is no output schema.

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?

No output schema and no annotations exist, so the description must cover both purpose and return shape — it enumerates every returned field and the snapshot for reuse. Quota, batching, and downstream chaining are all present; nothing essential for a correct call is missing.

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?

Only one parameter and schema coverage is 100%; the schema already says 'Up to 3 domains'. The description's 'Free for up to 3 domains per call' repeats the same constraint without adding format, normalization, or duplicate-handling guidance, so this is baseline.

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?

Uses a specific verb (audit) plus resource (sending domains) and enumerates exactly what the result contains: grade, SPF lookup count, DMARC policy, DKIM status, MTA-STS, TLS-RPT, BIMI and fixes. It also distinguishes itself from the sibling monitor_sending_domains by positioning its output as a snapshot to hand off later.

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?

'Free for up to 3 domains per call' signals this is the batched, one-shot audit path and implies larger lists must be chunked. The handoff 'snapshot to pass to monitor_sending_domains later' gives a clear workflow position, though no explicit when-not-to-use or comparison against inspect_domain_dns is stated.

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