ios_devices

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

readOnlyHint=true already tells the agent this is a safe read, so the description's only added value is naming the readiness states returned (booted / reachable). It does not clarify whether powered-off simulators are included, whether real devices are discovered over the network, or what ordering to expect.

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?

A single front-loaded sentence with the verb and resource first and the readiness qualifier second. Every clause earns its place; nothing is padded or repeated from the title.

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 zero-parameter, read-only list tool with no output schema, stating what is enumerated and what readiness means is essentially sufficient. A sentence on discovery mechanics (e.g., whether it requires Xcode/simctl or scans the network) would close the remaining gap.

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 tool takes zero parameters, so there is no parameter semantics to document and the baseline of 4 applies. The description correctly introduces no filtering concepts that might imply hidden arguments.

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 specific verb ('List') and concrete resources ('simulators and real iPhones'), plus the attribute surfaced (booted / reachable). It is clearly distinguishable from siblings like ios_apps, ios_boot, and ios_observe, which act on a device rather than enumerating devices.

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?

Usage is only implied: an agent can infer this is the discovery step before ios_boot/ios_observe, but the description never says 'call this first to obtain a device identifier' or name any alternative or exclusion. No prerequisites or conditions are given.

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