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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, and openWorldHint=false. The description adds valuable behavior beyond those: it arms a local reflex, watches the video stream, fires gamepad button 0 immediately, avoids a round trip, and returns fire/frame counts and server-side detect-to-write timing. It does not fully cover permission or rate-limit behavior, but the operational mechanics are well disclosed.

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 front-loaded with the core action and avoids obvious filler. It is slightly dense with a caveat about authoritative measurement, but each sentence contributes useful information about operation, return values, or interpretation.

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?

There is no output schema, so the description appropriately names what is returned: fire count, decoded frame count, frame intervals, and server-side detect-to-write time. It also warns that the authoritative end-to-end number must come from the device clock. For a complex timing probe, this is strong, though setup prerequisites such as gamepad or video-stream availability are not fully spelled out.

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 required parameters and defaults are already documented in the schema. The description adds contextual meaning for thresholdDelta ('brightness jump') and holdMs ('hold the button before releasing and re-arming'), but does not provide additional syntax or format details beyond 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?

The description uses a specific verb and resource: 'arm a local reflex on an Android device' that watches a video stream for a brightness jump and fires gamepad button 0. It clearly differentiates from sibling tools like device_gamepad_state, device_video_stream, or android_fps by describing a closed-loop latency probe rather than a simple state read or stream.

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 usage context is implied: it 'measures how fast the loop can close' and is labelled a SPIKE, which suggests latency/performance investigation. However, it does not explicitly say when to choose this over alternatives such as android_fps or device_gamepad_state, nor does it state prerequisites or exclusions.

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