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

With no annotations provided, the description carries full burden of behavioral disclosure, and it delivers richly. It reveals the internal mechanism (bundled locale-change helper with reflection into ActivityManagerNative.updateConfiguration), persistence behavior (survives reboot), and multiple caveats: Samsung One UI/MIUI may re-apply their locale, Android 14+ requires hidden_api_policy=1 (set automatically), and MDM-managed devices may refuse CHANGE_CONFIGURATION grant. This is comprehensive behavioral transparency.

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 a dense, well-organized paragraph of ~75 words covering purpose, mechanism, alternative, and caveats. Every sentence earns its place—there's no filler. Information is front-loaded with the primary purpose first, then the alternative, then caveats. This is efficient and effectively structured.

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 this is a persistent, device-wide mutation tool with no annotations and no output schema, the description is remarkably complete. It covers the action, persistence, mechanism, affects-all-apps scope, alternatives, and platform-specific caveats (Samsung/MIUI, Android 14+, MDM). For a tool of this complexity and side-effect profile, the description provides agent-burden-bearing context that fully compensates for the lack of annotations.

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 schema fully documents all 4 parameters (udid, language, country, script). The description adds implicit context about the language/country usage but doesn't add parameter-specific detail beyond what the schema states. Per the rubric, with high coverage the baseline is 3, and the description doesn't substantially augment parameter semantics.

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 purpose: 'Change the Android device's system language and locale' with explicit scoping (persistent, affects every app, survives reboot). It names the specific verb (change), resource (Android device's system language/locale), and key characteristics. It also distinguishes from sibling tool device_launch_app_in_language, which is named explicitly as the alternative for per-app testing.

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?

The description explicitly tells when to use it (change whole device) and when NOT to: 'For per-app testing without changing the whole device, prefer device_launch_app_in_language'. It names the alternative tool directly and gives clear directive. This meets the highest tier of usage guidance with explicit when/when-not/alternatives.

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