ios_open_session

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

Beyond the annotations, the description reveals important side effects: it boots the simulator or verifies the phone, starts WebDriverAgent, and opens a tuned session. The explicit note about default device preference — preferring a booted simulator over a connected iPhone — adds valuable behavioral nuance not available from annotations or schema.

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?

The description is compact, front-loaded with the core purpose, and every sentence adds value: one for overall intent, one for mechanism, and one for a critical selection caveat. No filler or redundancy.

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?

Given a fully described input schema, an output schema, and annotations that cover idempotency and side-effect hints, the description supplies the remaining operational context: setup steps and device-selection behavior. Nothing essential for an agent to correctly invoke and interpret this tool is missing.

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?

The schema already provides 100% description coverage for all three parameters, so the baseline is strong. The description adds meaningful semantics for `device` by explaining how the default is chosen, which is not fully specified 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?

The description leads with a specific action and resource: 'Attach to a device and start driving it.' It then details the concrete steps (boots simulator/verifies phone, starts WebDriverAgent, opens a tuned session), which clearly identifies it as the session-opening tool and distinguishes it from the interaction and lifecycle sibling tools.

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 provides clear context that this tool is the entry point for driving a device and explains the device-selection behavior. It does not explicitly name alternatives or exclusions, but the intended use is strongly implied by the first sentence and the device-preference caveat.

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