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

Goes well beyond the readOnly/openWorld annotations: discloses that computation is local to the Worker with no outside call, and states the exact price ($0.002 USDC via x402 on Base/Solana/Arc) with the important detail that failed calls are not charged. Cost and payment mechanics are critical behavioral facts an agent needs before invoking a paid 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?

Three tight sentences, front-loaded with the two capabilities and followed by execution model and pricing. No filler; every clause (including the failed-call billing rule) carries information an agent would otherwise have to guess.

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 all three parameters documented in the schema, an output schema present, and safety/pricing covered in the description, an agent has everything needed to select and invoke it correctly. Return value structure is rightly left to the output schema.

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 baseline is 3; the description adds real value by coupling the two optional parameters — conversion requires both time and to together, a constraint the schema does not express. It doesn't describe accepted time formats or zone validation beyond what the schema already shows.

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?

Names the resource (time in an IANA zone) and two precise operations: reporting current time plus UTC offset/DST status, and converting a local time between zones. The dual mode is spelled out with the exact parameters that trigger each, so an agent can distinguish it from siblings like date_calc or business_days without opening the schema.

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?

"with time and to, the conversion..." gives an explicit trigger condition for the conversion mode, implying zone-only means current time. However, it never names alternatives (date_calc, business_days, holidays) or states when not to use this tool, so routing to siblings is left to inference.

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