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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint, so the safety profile is covered. The description adds useful specifics about what is checked (DNS records, SPF, DMARC) and the outcome (overall health score), though it does not mention external DNS lookups or return details.

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 tightly written sentences, front-loaded with the core action and followed by the use case. No redundant or filler content.

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?

For a simple read-only diagnostic tool with one parameter, annotations covering safety, and no output schema, the description provides enough to invoke it correctly. It could optionally state what the health score represents or what the response includes, but the core purpose and checks are clear.

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 input schema has 100% description coverage for the single parameter, including an example. The description adds no further parameter guidance, which is acceptable since the schema already fully documents the field.

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 specific verb and resource ('Check the DNS and deliverability health of an email domain') and enumerates the exact checks (MX, SPF, DMARC, overall health score). Clearly distinguishes from sibling verification tools, which target individual email addresses rather than domain-level health.

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?

Provides clear context for when to use it ('diagnosing why a domain bounces' or 'validating a sending domain'), but does not mention explicit alternatives or when-not to use it, such as deferring to verify_email for individual address checks.

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