Start a countdown timer in the phone's Clock app without opening the app. Specify seconds and an optional label to time tasks, cooking, or reminders.
Start a countdown timer in the phone's Clock app, without opening it.
| Name | Required | Description | Default |
|---|---|---|---|
| label | No | Optional: what it's for | |
| seconds | Yes | Length in seconds (1 to 86400) |
Changes observed during successful MCP inspections.
v2.2.21Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden, and it does add one useful behavioral trait: the timer starts 'without opening' the Clock app, signaling a non-intrusive background action. It does not say whether this replaces a running timer, what confirmation is returned, or any permission/device constraints.
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 tight sentence with the action front-loaded and zero filler; the 'without opening it' clause earns its place by adding behavioral value.
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 two-parameter tool with full schema coverage and no output schema, the description is close to complete: purpose and the key side-effect (no app switch) are covered. Minor gaps remain around timer-replacement behavior and result confirmation.
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%, with both 'seconds' (range 1–86400) and 'label' fully documented in the schema. The description adds no parameter detail beyond that, so baseline 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 ('Start a countdown timer in the phone's Clock app'), and the word 'countdown' implicitly separates it from the sibling set_alarm. However, it never names set_alarm, so an agent must infer the distinction from semantics rather than being routed explicitly.
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 'countdown timer' — an agent can infer it's for elapsed-time needs rather than alarms. No explicit when-to-use, when-not-to-use, or 'use set_alarm instead for absolute times' guidance is given.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.