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

No annotations are provided, so the description carries the full burden. It discloses that the tool takes 10-30 seconds to launch, which is useful behavioral context, and implies it initiates a persistent session. However, it does not disclose what happens on failure, or how to cleanup (though the sibling ios_end_session 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?

Two short sentences with no filler. The critical sequencing constraint is front-loaded, and the latency note is a useful addition. Very efficient.

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 session-start tool with a single parameter, the description is adequate. It covers the prerequisite, the latency, and implicitly the need for a session before other commands. The only gap is not describing the session handle output, but since there is no output schema, the agent may infer it from the tool's success.

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 description does not need to add parameter meaning. The udid parameter is adequately described in the schema, and the description does not add extra syntax or format details. Baseline 3 is correct.

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 clearly states the tool starts an iOS automation session on a deviceaine, which is a specific verb and resource. It distinguishes itself from siblings by being a session lifecycle tool, but does not explicitly differentiate from ios_end_session or other session-related tools like automation_session_create.

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?

It explicitly states it must be called before any iOS control commands, providing a clear precondition. It implies the alternative is ios_end_session, but no exclusions are given, so a 4 is appropriate.

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