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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds the matching semantics of display-name resolution but says nothing about what happens if the app is already running, if the package is not installed, or if a display name matches multiple apps.

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 the core action front-loaded and no filler. The final sentence is partially redundant with the parenthetical in sentence two, which keeps it just short of ideal.

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?

There is no output schema, and for a simple launch action the description is nearly sufficient. However, it omits the failure/ambiguity behavior an agent needs to act on (uninstalled package, multiple substring matches, no return info), leaving a meaningful gap for a mutation tool.

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 both parameters are already documented in the schema, and the description largely restates them (package name or display name, case-insensitive substring). It adds an illustrative example ("Chrome") but no extra syntax, normalization, or ambiguity-resolution rules, 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 concrete verb and resource ("Launch an Android app") and the platform qualifier implicitly separates it from ios_launch_app. It does not name or contrast any sibling (device_launch_app_in_language, device_terminate_app), so differentiation relies on the reader scanning the tool list.

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 explains accepted input formats but never says when to use this tool versus alternatives such as device_launch_app_in_language or how it relates to device_terminate_app/device_list_apps. No prerequisites (app must be installed, device must be connected) or when-not-to-use guidance is given.

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