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

With annotations indicating read-only, idempotent, and non-destructive, the description adds value by explaining the scoring methodology in detail (e.g., SPF score mapping, DMARC policies, DKIM selectors). It also notes the live DNS check via Cloudflare DoH with no cache, which is useful behavioral context beyond the 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?

The description is highly detailed and well-structured, using bullet points for scoring criteria and a clear example. It is longer than a one-liner but every sentence adds value, explaining return fields and scoring rules. It is verbose but appropriate for the tool's 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?

Given the complex scoring logic and the presence of an output schema, the description comprehensively explains the domains, scoring criteria, return fields, and example usage. An agent can accurately call the tool and interpret results without needing additional external documentation.

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 covers the domain parameter fully with description and format examples. The tool description reiterates the parameter format but doesn't add significant new semantics beyond what the schema already provides. Since coverage is 100%, a baseline of 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?

The description explicitly states the tool checks SPF, DMARC, and DKIM email authentication for a domain, which is a specific verb and resource. It clearly distinguishes itself from sibling tools like domain_fetch_dns_records by focusing on security scoring rather than raw DNS records.

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?

The description includes a clear example of usage and specifies the domain format. It doesn't explicitly mention when not to use it or list alternatives, but given the domain-specific nature and the example, it provides sufficient context for an agent to know when to invoke it.

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