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

Annotations already declare readOnly, idempotent, and closed-world, so the safety profile is covered. The description still adds real behavioral context beyond them: it will not start a network scan and, importantly, that a missing record is not proof a domain is unsafe — a caveat an agent needs to avoid drawing wrong conclusions.

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?

Three short sentences, front-loaded with the core purpose, then the behavioral exclusion, then the interpretation caveat. Every sentence carries information and nothing is padded.

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 read tool with no output schema, the description supplies the returned fields and the stale/undetermined/not_scanned state vocabulary plus the missing-record caveat. An agent has everything needed to call it 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 has full 100% description coverage for the single 'domain' parameter, including the HTTPS-443-only constraint, so the description adds no parameter meaning. The fields it lists (checked_at, expires_at, states) are return values rather than parameter semantics, so the baseline 3 applies.

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 opens with a specific verb+resource ('Read existing TLS evidence') and enumerates the fields returned (source, checked_at, expires_at, and the four states). It also distinguishes itself from the scanning sibling via 'Never starts a new network scan', so an agent can tell it apart from scan_tls without opening a schema.

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?

Usage is clearly implied — read already-stored evidence — and there is an explicit exclusion: it never triggers a new scan, which routes scan-triggering intent to scan_tls. It stops short of naming scan_tls or spelling out the 'if you need fresh data, use X' condition, so it is not fully 5-level routing guidance.

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