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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains that the tool operates without a round trip, watches a video stream, fires gamepad button 0, and returns specific metrics. It even warns that the detect-to-write time measured server-side is not authoritative and that the real end-to-end number must come from the device clock. It does not mention side effects of firing the gamepad button or whether a video stream must be running first, but the disclosed internals and limitation go well beyond a minimal statement.

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?

The description is dense and front-loaded, beginning with the core action and then moving to return values and a caveat. Every clause adds information, but the multiple dashes and the 'SPIKE' prefix make it slightly harder to parse at a glance. Still, nothing feels wasted.

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?

The description lists the key return values (fire count, decoded frame count, frame intervals, detect-to-write time) and the critical device-clock caveat, which is useful since there is no output schema. However, it does not specify return formats, does not mention a prerequisite like starting the video stream first, and omits any caution about the gamepad button firing as a side effect. Given the tool's complexity and lack of annotations, this is adequate but not complete.

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?

The schema has 100% description coverage for all four parameters, including udid, holdMs, durationMs, and thresholdDelta. The description does not add meaningful parameter-level detail beyond 'brightness jump', which loosely maps to thresholdDelta. Since the schema already documents the parameters thoroughly, the baseline of 3 is appropriate.

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 description starts with a specific verb and resource: 'arm a local reflex on an Android device' and immediately details the exact mechanism: watch the video stream for a brightness jump and fire gamepad button 0. It clearly states what it measures ('how fast the loop can close') and is distinct from any sibling tool by describing a unique local-reflex probe rather than a generic screenshot, stream, or performance capture tool.

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?

The description implies the tool is for measuring local reflex latency and provides a critical caveat about the authoritative end-to-end number needing to come from the device clock. However, it never states when to prefer this tool over other performance-related siblings like android_fps, android_performance_record_start, or device_record_start, nor does it name explicit alternatives or exclusions.

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