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

With no annotations available, the description carries the full behavioral burden. It discloses bidirectional conversion, input selection via query parameters, and even the HTTP price. It does not cover edge cases like invalid input or what happens if both ts and iso are supplied, but the core behavior is transparent.

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?

The description is a single compact line that front-loads the core functionality and immediately follows with concrete invocation examples. Every element, including the price note, earns its place without redundant prose.

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 simple conversion tool with an output schema available, this description is nearly complete: it defines the conversion direction, query parameters, and cost. The main missing piece is explicit guidance on parameter exclusivity or default behavior when neither ts nor iso is provided, but this is a minor gap given the simplicity.

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 input schema has 0% parameter descriptions, so the description compensates by naming and exemplifying both relevant parameters, including the ?iso parameter that is absent from the schema. It adds meaningful format context beyond the bare schema, though it could be more explicit about types and mutual exclusivity.

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 clearly states the tool's purpose: converting Unix timestamps to ISO8601 and back. The 'both ways' phrasing and explicit query-param examples leave no ambiguity about what resource this tool acts on and how it distinguishes itself from the converter siblings.

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 usage is strongly implied through the examples: pass ?ts= for Unix to ISO conversion and ?iso= for ISO to Unix. However, there is no explicit when-to-use guidance or mention of alternatives, so an agent must infer the appropriate context from the examples alone.

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