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

The description thoroughly explains behavior beyond annotations: it resolves a TXT record, fetches from a well-known URL, includes a timeout, and defines four possible return statuses with their semantics. This is rich operational detail that annotations (readOnlyHint, openWorldHint) do not cover.

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 compact yet information-dense, covering the process, protocol, timeout, and return formats in a few sentences. It is front-loaded with the key action and outcome, making it easy for an agent to parse quickly.

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?

The tool has a single parameter fully documented, annotations for safety, and no output schema, so the description must define return values—and it does comprehensively. The agent has everything needed to call and interpret the result.

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 already documents the domain parameter at 100% coverage, including constraints on IP addresses and paths. The description adds no new parameter-specific detail, so a baseline score of 3 is appropriate given the schema's completeness.

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 the tool fetches and validates a domain's MTA-STS policy, specifying the exact records and endpoints involved. It distinguishes itself from sibling DNS/email security tools by focusing specifically on MTA-STS policy validation.

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 explains the tool's purpose for confirming TLS delivery requirements and lists distinct return statuses that help the agent interpret results. However, it does not explicitly state when not to use this tool or name alternative siblings for similar tasks.

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