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

Beyond the annotations it discloses DST handling, the 10-zone conversion cap, per-call pricing ($0.01 via x402 USDC or card key), the 25 free calls, and that failed calls are free. It also explains why repeats cost money, which is exactly the context an agent needs to interpret idempotentHint=false on an otherwise read-only tool.

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?

Core capability, usage triggers, example and pricing are front-loaded in a logical order. The x402/MPP client-test sentence and the /credits parenthetical lean promotional and dilute focus, though they do carry payment-relevant information.

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 3-optional-parameter read tool with no output schema, the definition covers defaults, limits, DST behavior, billing, and failure cost. An agent has everything needed to call it correctly and to anticipate the cost of repeating a call.

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 100%, so zone, at and to are already fully documented, and the description mostly restates them (UTC default, max 10 zones). It adds only a concrete example (zone=Europe/Stockholm) and the framing that 'to' converts the same moment. That is marginal added meaning over 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?

The first sentence names a specific resource and verb: exact current date and time in any IANA time zone, plus UTC offset, weekday, abbreviation and Unix timestamp, with optional multi-zone conversion. This is unmistakably distinct from siblings like sun, moon, or holidays, which share the temporal domain but not the function.

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?

It gives explicit when-to-use triggers: knowing the current time, scheduling across time zones, and turning a timestamp into local time. It also flags a secondary use case (paid end-to-end client test). No when-not guidance or named alternative is offered, but no sibling actually overlaps enough to require one.

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