Email MX

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

Goes beyond annotations by explaining DKIM status logic ('verified' vs 'unverifiable'), grading formula under both DKIM conditions, and that DKIM absence is not penalized. Also mentions rate limits. No contradictions with annotations.

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?

Starts with core purpose, followed by alternative, rate limits, and detailed behavioral notes. Each sentence adds value. Slightly long but well-organized and front-loaded.

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?

Covers what the tool returns (list of fields) and explains grading and DKIM logic. The 'issues' field is mentioned but not detailed, which is acceptable with output schema present. Adequate for the tool's complexity.

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 provides clear description for the only parameter 'domain'. The tool description adds no further parameter meaning; baseline 3 applies since schema coverage is 100%.

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?

Clearly states the tool analyzes email security covering MX records, SPF, DMARC, DKIM, mail provider, and grade. Distinguishes from sibling 'domain_report' by specifying this is for verification and phishing risk while domain_report is for full audit.

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 says to use for verifying email-auth setup and phishing risk, and for full audit use domain_report. Provides rate limits but does not mention other siblings like email_security_posture. Clear context with one alternative.

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