Start a phone

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

With no annotations, the description carries the full load, and it does disclose two useful traits: it installs missing dependencies and it is idempotent/reuses an existing phone. It does not mention that boot can be slow, what state the phone is left in after boot, whether only one phone can run at a time, or how failures surface.

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?

Two tight sentences: the core action and its install behavior come first, then the sizing options, then the reuse note. Every clause carries information an agent needs to choose parameters.

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 7-parameter, annotation-free mutation tool with no output schema, the description covers what to pass and what side effects to expect. The remaining gap is the return value — the agent doesn't know whether it gets a device id or handle back, nor how long boot takes.

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 coverage is 100%, so the baseline is 3, and the description exceeds it by listing the actual allowed values for `device` (pixel-8, pixel-8-pro, small-phone, compact, tablet), which the schema does not enumerate. It adds nothing for `wipe`, `headless`, or `android`, but those are already documented in 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?

States a concrete verb and resource ('Boot an Android phone') plus a distinguishing detail that it installs anything missing first, which separates it from phone_stop and phone_install in the sibling list. It also enumerates the supported device profiles, so an agent knows the valid domain without opening the schema.

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?

Explains the two selection paths — pick a named profile or pass width/height/density — and notes that an already-running phone is reused, so the agent needn't call phone_list first. It stops short of explicit when-not guidance or naming an alternative (e.g., when to prefer a separate install/boot flow).

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