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

The annotation readOnlyHint=true already covers the safe-read nature. The description adds substantive behavioral context: 'Each leg fails soft and is reported independently,' which tells the agent that failures in one check won't prevent others from reporting. This goes beyond the annotation and helps set expectations without contradicting it.

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 packed sentences with no filler. The opening 'Check the live SSL/TLS certificate...' immediately communicates the primary action and object, and the second sentence adds critical behavioral nuance without redundancy.

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 single-parameter tool with three independent checks and no output schema, the description is largely sufficient. It states the three legs and the soft-fail reporting, which implies a structured response. The only gap is the exact return format, but the description allows an agent to invoke correctly and infer result independence.

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?

Schema coverage is 100%—the hostname parameter is described as 'A public hostname, e.g. example.com.' The description reinforces 'any public hostname' but doesn't add new details about format, normalization, or edge cases. The baseline of 3 is appropriate since the schema carries the meaning.

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 uses the specific verb 'Check' and clearly enumerates the three distinct checks: SSL/TLS certificate (validity, expiry, issuer), DNS records (A/AAAA/MX/NS), and RDAP expiry. This differentiates it from sibling health check tools like check_mcp_health and check_agent_readiness, making it unambiguous what the tool does.

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 states it works on 'any public hostname' and notes that each leg 'fails soft and is reported independently,' implying a diagnostic scenario where partial failures are tolerated. While it doesn't explicitly compare to alternatives, the scope and behavior clearly signal when to use this tool (domain health assessment) versus check_mcp_health or check_agent_readiness.

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