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

Annotations already declare it read-only, idempotent, non-destructive and closed-world, so the description needn't restate safety. It does add real behavioral context beyond them: the seconds-vs-milliseconds input tolerance, the 'now' sentinel, and the fact that output covers both forms. What's missing is how an ambiguous numeric value (e.g. 10 digits vs 13) is disambiguated.

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?

One front-loaded sentence that covers the verb, the accepted inputs, the output guarantee, and the 'now' special case. No filler and nothing buried.

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 converter with no output schema, the description supplies the accepted input domain and enough of the return shape ('both forms') to call it confidently. A note on invalid-input behavior or the exact output structure would close the last gap.

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 0% and the single string parameter is completely bare in the schema, so the description must carry the load — and it does, enumerating Unix seconds, Unix milliseconds, ISO date, and the literal 'now'. It stops short of specifying the accepted ISO format variants or precision details.

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?

A specific verb ('Convert') plus a specific resource (Unix timestamp / ISO date) with the accepted input forms named inline. It implicitly separates itself from siblings like date_difference and calculate_age by being a pure format conversion, though it does not name those siblings explicitly.

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 only implied: the described input formats make it clear this is the tool for normalizing a timestamp, and 'now' is flagged as a valid shorthand. There is no explicit statement of when to prefer this over date_difference or calculate_age, and no guidance on invalid input.

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