Start Screen Recording

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

Annotations already declare non-read-only, non-destructive, non-open-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: the recording persists in the background, must be explicitly stopped, and the return value is a save path rather than the recording itself. It omits edge cases such as behavior when a recording is already active or any storage/permission 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?

Three short sentences, front-loaded with the action, then the lifecycle, then the return value. No filler or repetition of the schema.

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?

With no output schema, the description usefully explains the return value (the path where the recording will be saved) and the stop counterpart, which is what an agent needs to call it correctly. Minor gaps remain around concurrent recordings and failure behavior.

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 device, output, and timeLimit are fully documented in the schema, including the .mp4 requirement and auto-stop semantics. The description adds no parameter detail beyond the schema, so the 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+resource ("Start recording the screen of a mobile device") and names the paired sibling mobile_stop_screen_recording, distinguishing it from screenshot tools like mobile_take_screenshot.

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 describes the lifecycle: it "runs in the background until stopped with mobile_stop_screen_recording", which tells the agent this is a paired start/stop operation. It does not, however, say when to prefer recording over mobile_take_screenshot or mobile_save_screenshot.

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