previewapk_start

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

With no annotations, the description carries the full burden. It usefully discloses that in driver='user' mode the agent's input is refused and points to where session links come from, but it omits preconditions, what state a start creates or overwrites, permission requirements, and what happens if a session already exists.

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 front-loaded sentences with little waste: purpose first, then the driver semantics, then the return/next-step guidance. All earn their place, though the final sentence about session_url is slightly tangential to the start action itself.

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?

No output schema or annotations exist, so the description must stand alone. It covers the action, the key parameter's semantics, and the high-level return flow (links info), which is enough for correct invocation, though the 'device' parameter and the exact return shape remain unspecified.

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 0%, so the description must compensate. It does an excellent job on the driver enum (clearly defining agent vs user behavior), but the required 'device' parameter is never explained — no format, ID source, or relationship to previewapk_list_devices — leaving half the parameters semantically undocumented.

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?

"Start a preview session for the device's attached app" is a specific verb+resource that clearly distinguishes it from previewapk_stop and the action siblings (tap/swipe/type). However it never explicitly clarifies its boundary against previewapk_relaunch or previewapk_use_device, both of which also relate to getting an app running, so differentiation from those siblings is left to inference.

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 explains the agent vs user driving modes well, but that is parameter selection guidance rather than when-to-call-this-tool guidance. There is no statement of preconditions (e.g. does a device need to be selected first via previewapk_use_device) or when to prefer this over relaunch, so usage is only implied.

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