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

With no annotations present, the description carries the full burden and does disclose two non-obvious traits: that the call is paid (pay-per-call $0.001 USDC) and exactly what the response contains. It stops short of covering error behavior or failure modes (e.g. invalid timezone or unparseable input).

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 tight sentences, front-loaded with the core action and input/output contract. The trailing endpoint path and price are compact and useful, though the endpoint path adds little for an agent selecting the tool.

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 two-parameter tool with no output schema, the description correctly compensates by spelling out return values and the timezone targeting, and adds the cost model. Only failure/error semantics remain uncovered, which is a minor gap for a pure conversion utility.

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 description coverage is 100%, so the schema already documents both parameters fully; baseline is 3. The description restates the accepted value formats (seconds, ms, ISO) rather than adding syntax or edge-case detail beyond the schema.

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 precise verb+resource (convert between unix epoch and human time) and enumerates both accepted inputs (seconds, milliseconds, ISO date) and produced outputs (epoch s+ms, ISO-8601 UTC, timezone-formatted value). This makes it clearly distinguishable from generic siblings like unit_convert without opening their schemas.

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 implies usage by describing the input/output contract, but never states when to choose this tool over alternatives such as unit_convert, nor any exclusions or preconditions. Context is implied rather than explicit.

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