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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=false, so the safety profile is covered. The description adds value beyond them with a real precondition ('Requires Android 13+') and the post-condition (fallback to system language), though it does not state whether the app must be relaunched for the change to take effect.

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 with zero filler: effect first, then the sibling relationship, then the platform requirement. Every sentence carries information an agent needs and nothing is buried.

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 two-parameter, no-output-schema tool with rich annotations, the definition covers the effect, the alternative, and the OS floor. The one missing piece is whether the locale change takes effect immediately or only after relaunching the app.

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 100%, so udid and packageName are already fully documented in the schema. The description says 'an Android app' without adding format or constraint detail beyond what the schema provides, so the baseline of 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?

States a specific verb ('drop') and resource ('per-app locale override') plus the resulting state ('falls back to the device system language'), which makes the outcome unambiguous. It also names the counterpart tool, device_launch_app_in_language, so an agent can separate it from device_set_device_language and other locale siblings without opening a schema.

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?

Naming device_launch_app_in_language as the counterpart gives a clear implied usage pattern: this is the undo/reset path after a per-app language was applied. It gives clear context but stops short of explicit when-not conditions (e.g. use device_set_device_language to change the whole device locale).

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