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

Goes well beyond annotations by disclosing the implementation approach (bundled locale-change helper with reflection into ActivityManagerNative.updateConfiguration), persistence/survival across reboot, OEM re-application caveats (Samsung One UI / MIUI), Android 14+ hidden_api_policy requirement, and MDM refusal possibility.

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?

Front-loads the core purpose, then alternatives, then caveats in a logical order. Three dense sentences; every clause contributes, though a bit packed. Slightly long but no filler.

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?

No output schema, but the description covers behavior, persistence, failure modes, and the read/write profile is clear from annotations. Return-value expectations are not spelled out, which is a minor gap for a mutation tool that presumably reports success/failure.

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 the schema already documents all four parameters including the optional 'script' tag. The description adds no additional parameter-level detail (no examples or format constraints beyond the schema), 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?

Specific verb+resource ('Change the Android device's system language and locale') with scope clarified as system-wide, persistent, and reboot-surviving. It explicitly distinguishes itself from device_launch_app_in_language 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?

Names the alternative (device_launch_app_in_language) and the condition selecting it (per-app testing without changing the whole device). It also states prerequisites/constraints (hidden_api_policy=1 on Android 14+, MDM grants), giving explicit when-to-use and when-not guidance.

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