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

Goes beyond the annotations by explaining the surprising readOnlyHint=false: 'Reads or computes only; not marked read-only because each call is charged.' It also discloses pricing ($0.002/call via x402 USDC or card key, first 25 free, failed calls free) and that DST is handled — behavioral context an agent cannot derive from the annotation block.

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?

Front-loaded with the core capability, then optional conversion, then usage, then an example, then commercial terms — a sensible ordering. Dense but each sentence carries information; the pricing sentence is long but materially affects whether an agent should call it.

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?

No output schema exists, and the description compensates by naming the returned fields (UTC offset, weekday, abbreviation, Unix timestamp). With only three params, one required, plus the example and pricing, an agent has everything needed to call it correctly.

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, but the description adds a concrete worked example (zone=Europe/Stockholm, at=2026-03-01T09:00:00+01:00, to=America/New_York,Asia/Tokyo) demonstrating format and comma-separated multi-zone usage. It also notes the 'max 10' and default-to-now semantics, adding real value 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?

States a specific verb and resource — 'the exact current date and time in any IANA time zone' plus optional conversion into up to 10 other zones. The return payload is enumerated (UTC offset, weekday, abbreviation, Unix timestamp), which no sibling (sun, moon, holidays) offers, so the agent can distinguish it immediately.

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?

Explicitly names three triggering scenarios: needing to know the current time, scheduling a meeting across time zones, and converting a timestamp to local time. No when-not guidance or named alternative is given, but the sibling set makes the boundary obvious, so this stops just short of a 5.

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