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

The description fully discloses the tool's behavior beyond the readOnlyHint and openWorldHint annotations. It specifies the underlying query mechanism (Cloudflare DNS-over-HTTPS), the JSON response structure with all possible statuses (ok, not_applicable, timeout, error), and provides interpretive guidance (treat not_applicable as a finding, error as unknown). This is exemplary behavioral transparency.

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 information-dense but not padded. The primary purpose is front-loaded in the first sentence, followed by a concise explanation of return statuses. It avoids unnecessary details while covering all essential aspects. It could be slightly trimmed, but every sentence earns its place.

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 tool's moderate complexity, no output schema, and a single parameter, the description is complete. It explains the return format thoroughly, distinguishes genuine absence from errors, and notes the use of Cloudflare DNS-over-HTTPS. An agent has everything needed to call the tool and interpret results correctly.

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 schema description coverage is 100%, fully documenting the 'domain' parameter with format restrictions (no IPs, ports, paths, prefixes). The tool description adds no additional parameter-level information beyond what the schema already provides, so the baseline score 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 clearly states a specific action ('Look up a domain's SMTP TLS Reporting policy'), the exact DNS record queried (_smtp._tls.<domain>), and the intended use case (confirm the domain receives reports). This distinguishes it from sibling dossier tools, which target different record types or surfaces, even without naming them.

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 provides explicit context for when to use the tool: 'Use to confirm the domain receives reports about failed TLS delivery of its inbound mail.' It does not name alternative tools, but given the unique purpose among siblings, this is sufficient. It could be more explicit about when NOT to use it, but the purpose is clear enough for an agent to select it appropriately.

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