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

Annotations already declare readOnly/openWorld/non-destructive/non-idempotent, and the description usefully adds that unit detection is automatic, that omitting input returns now, and that every call is billed (failed ones free) — which explains the non-idempotent hint. It stops short of describing output shape or precision/timezone handling.

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?

Conversion semantics and the no-input default are front-loaded, then usage, then an example. The pricing sentence is somewhat promotional but is genuinely decision-relevant since calls cost money.

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 one-parameter pure-compute tool with no output schema, the description covers input forms, defaults, unit detection, and cost. Minor gaps remain around output format details and timezone assumptions.

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?

With a single parameter at 100% schema coverage, the schema already carries the baseline. The description still adds real meaning: seconds vs milliseconds are auto-detected, ISO date strings are accepted, and a concrete example (value=1792281600) is supplied.

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 and resource with both directions spelled out (timestamp→ISO date, ISO date→timestamp) plus the no-input default, so the operation is unambiguous. It never names the nearby siblings (date_info, date_add, date_diff), so an agent must infer the boundary itself.

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 to read timestamps in logs and APIs" gives concrete invocation context, and the no-input case is explicitly defined. There is no when-not guidance and no explicit alternative named for date arithmetic versus simple conversion.

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