Calculate how long remains until a target or deadline, or how much time has passed since it. Provide an ISO 8601 moment to get the exact countdown or elapsed duration.
倒计时：计算距离目标/截止时刻还剩多久（目标已过则返回已过时长）。
| Name | Required | Description | Default |
|---|---|---|---|
| from | No | 从哪个时刻开始算（ISO 8601），缺省为当前时刻 | |
| target | Yes | 目标时刻，ISO 8601（如 2026-10-01T15:30:00 或 2026-10-01 15:30:00） | |
| timezone | No | target 不带偏移时按此时区解释为墙钟时间；缺省用系统时区 |
Changes observed during successful MCP inspections.
v0.2.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It usefully discloses that a past target yields the elapsed duration instead of an error, which is a real behavioral trait. But it says nothing about how the result is formatted, how from/timezone interact, or error handling for invalid input.
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?
A single compact sentence, front-loaded with the core action and parenthetically covering the inverted-case behavior. Every clause earns its place with no redundancy.
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 3-parameter tool with no output schema and no annotations, the description omits the return type/format and the from/timezone interaction. It is minimally adequate but leaves the agent guessing about output shape and edge-case semantics.
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 all three parameters (from, target, timezone) are already documented with formats and defaults in the schema. The description adds no parameter-level detail beyond that, so the baseline of 3 applies.
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 ('計算距離目標/截止時刻還剩多久') plus the edge case when the target has passed. An agent can immediately tell this computes a countdown, though it doesn't explicitly contrast with the closest sibling duration_elapsed.
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?
Usage is implied by the countdown-to-a-deadline framing ('目標/截止時刻'), which gives an agent enough to know the context. However, no explicit when-to-use or when-not guidance is given, and no alternatives are named despite siblings like duration_elapsed and timezone_convert that overlap conceptually.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.