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

Beyond the readOnly/destructive annotations it discloses real limits: uses DNS and policy-file lookups, never changes DNS, and does not guarantee inbox placement. It also notes fresh=true bypasses cached results, which an agent cannot infer from annotations alone.

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 are front-loaded with the purpose before usage, parameters, and return/limits. Dense but each clause earns its place; no 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 usefully enumerates what is returned (graded scorecard, findings, proposed DNS fixes, report permalink) and states the tool's operational bounds. An agent has enough to invoke it correctly and set expectations.

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 description coverage is 100%, so all four parameters (domain, checks, dkim_selectors, fresh) are already documented. The description only restates 'optional checks and DKIM selectors, and fresh=true,' adding no syntax or default detail beyond the schema, so baseline 3 applies.

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 precise verb (audit/diagnose) and resource (a domain's SPF/DKIM/DMARC/MX/BIMI/MTA-STS/TLS-RPT configuration), enumerating the exact check surface. It is clearly distinguishable from siblings like generate_dns_records or analyze_email_headers.

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?

Explicitly frames the trigger condition: 'when troubleshooting email authentication or spam delivery.' It gives a clear context for use but does not name which sibling to prefer when, e.g., analyzing headers vs. diagnosing a domain.

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