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

Goes far beyond the read-only annotation by explaining the honest DKIM evidence policy (verified only if a selector responds, else unverifiable), the grading logic's dependence on DKIM verifiability, and that DKIM absence is not penalized. This prevents misinterpretation of results. Rate limits are also disclosed.

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?

The description is dense and front-loaded with the core purpose, then adds necessary detail on DKIM semantics, grading rules, and return structure. It is somewhat long but every sentence carries distinct value; the semicolon-separated lists keep it readable. Not overly verbose for the complexity.

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 the return object shape, the DKIM evidence edge case, the grading algorithm in detail, rate limits, and directs to a more comprehensive sibling. With an output schema present, the description still adds substantial context, making the tool fully self-contained for an agent.

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?

The single parameter 'domain' is already fully described in the schema with examples. The description adds no new parameter syntax or constraints, so baseline 3 is appropriate given 100% schema coverage.

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?

The description states a specific action ('Analyze email security') followed by the exact resources analyzed (MX, SPF, DMARC, DKIM, provider, grade). It names sibling tool domain_report to draw the boundary, making its purpose unambiguous.

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 when to use it ('verify email-auth setup and phishing risk') and directs users to domain_report for a full audit. Also includes rate-limit context, helping agents decide whether to call it under resource constraints.

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