check_mta_sts

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

Annotations provide readOnlyHint=true and idempotentHint=true, and description augments with concrete behavior: queries `_mta-sts.<domain>`, fetches policy file, reports mode and MX coverage. Says 'only' for current policy fetch, transparent about scope.

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?

Two dense sentences are well-structured, opening with the purpose, then mechanics, then usage guidance and sibling distinction. No wasted words.

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 the simple read-only DNS check with schema coverage and annotations, the description fully covers what is checked, why, how to contrast with related tools, and context within scan_domain audit.

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 already describes all three parameters at 100% coverage. Description does not add substantial parameter-level meaning beyond what schema provides, so baseline 3 is appropriate.

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?

Description clearly states it checks MTA-STS for inbound SMTP TLS enforcement, specific verb 'check' with resource (_mta-sts DNS record and policy file), and distinct from check_dane. It reports mode and MX coverage, so highly specific.

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 states use case: 'Use to verify whether inbound SMTP is protected against TLS downgrade or MITM' and calls out the alternative check_dane using TLSA pinning, clearly distinguishing when this tool is appropriate.

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