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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description meaningfully adds "Unauthenticated" (an auth requirement not captured by annotations) and pins the return precision to milliseconds.

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 return value and unit, then the usage trigger, then the auth note. The trailing "Examples: Current server epoch ms" adds little but wastes only a few tokens.

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 no-argument utility with an output schema, annotations covering safety, and both unit and auth disclosed in the description, an agent has everything needed to call and interpret it. Nothing material is missing.

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?

Zero parameters, so there is nothing for the description to disambiguate. The baseline of 4 applies; the epoch-ms detail usefully pins the return format even though it is not a parameter.

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?

States a specific verb (Return) and resource (protocol server wall-clock time) with explicit unit (Unix epoch milliseconds). No sibling tool overlaps this capability, so the agent can select it unambiguously.

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?

"Use before quoting to measure client clock skew" gives a concrete trigger condition for calling it. It doesn't name alternatives or exclusions, but no sibling performs this function, so the omission is minor.

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