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

With no annotations, the description carries the full burden and does well: it discloses that the call blocks until the phone is ready and returns the first screen, and that cloud Android is the default while iOS and real devices are early access. It leaves out failure modes (what happens if readiness times out) and cost/session implications, which keeps it short of a 5.

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 what the tool does and its blocking behavior, with defaults and early-access caveats after. Every sentence is useful; the phrasing of the isolation advice is slightly informal but not wasteful.

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, zero-required creation tool with no output schema, the description supplies the key missing piece: the return value ('its first screen') and the synchronous readiness wait. Timeout and lifecycle semantics live in the schema, so remaining gaps are minor.

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 86%, so the parameters are already documented, including the early-access enum behavior for device and platform. The description reinforces the platform/device defaults but adds no format or interaction 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?

The description uses a specific verb and resource ('Create a phone') and adds meaningful outcome detail: it waits until the phone is ready and returns its first screen. It does not differentiate from the sibling 'start_phone', so an agent must guess whether creating and starting are distinct operations.

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?

'Give each task or end user its own phone' gives a usage principle that implies isolation per workload. However, there is no explicit when-not guidance and no routing to alternatives such as list_phones (to reuse an existing phone) or start_phone, which a caller would need to choose correctly.

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