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

No annotations are provided, so the description carries the full burden. It does add a useful non-obvious cost signal (1 credit) and implies a pure read/compute operation, but it says nothing about the return shape (two rendered datetimes? offsets?), DST edge cases, or what happens with an invalid IANA zone.

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 short sentences, with the action front-loaded and the credit cost appended as a compact parenthetical. Nothing is redundant or padded.

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?

With three parameters, no annotations, and no output schema, the definition should say more about what comes back and how zone/DST errors are handled. The purpose and cost are covered, but an agent cannot fully predict the response from this text alone.

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 IANA zone and ISO 8601 semantics are already documented in the schema. The description only loosely echoes them via "ISO datetime in two time zones" and adds no format examples or constraint details beyond that baseline.

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 ("Show") and resource ("an ISO datetime in two time zones"), which is enough to distinguish it from a pure clock lookup. It does not name or contrast with the sibling time_now, so an agent must infer the boundary between 'convert this datetime' and 'get current time'.

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?

There is no explicit when-to-use guidance and no mention of alternatives such as time_now, even though that sibling is the most likely confusion point. The only cue is the implicit framing of converting an existing datetime rather than retrieving the current one.

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