check_mta_sts

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. Description adds DNS query and policy fetch but doesn't elaborate on caching behavior or rate limits. Given annotation coverage, description adds some value but not critical.

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 well-structured sentences. Purpose, method, usage guidance, and sibling distinction all included without redundancy. Front-loaded with key action.

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 moderate complexity, full schema coverage, output schema, and clear annotations, the description is complete. It explains what the tool does, how it works, what it reports, and how it differs from related tools.

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?

All parameters have descriptions in input schema (100% coverage). Description mentions 'reports mode and MX coverage' but does not add significant meaning beyond schema. Baseline score of 3 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 verb+resource: 'Check whether a domain enforces SMTP TLS for inbound mail via MTA-STS'. Specifies mechanism (queries _mta-sts.<domain>, fetches policy), output (mode, MX coverage), and explicitly distinguishes from sibling check_dane.

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?

States use case ('verify whether inbound SMTP is protected...') and explicitly distinguishes from check_dane. Does not include when-not-to-use or additional prerequisites, but the context is clear.

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