open_app

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

With no annotations, the description carries the full behavioral burden, yet it says nothing about what 'launch' entails (foregrounding an installed app, waiting for startup, behavior on failure, error returned if the package is missing). Only the surface action is disclosed.

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 no filler, which is appropriate in shape. It is arguably too terse for a tool with unannotated side effects, but there is no wasted text.

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, no annotations, and an undocumented 'package' parameter leave significant gaps: return value, failure modes, device-selection defaults, and whether the call blocks are all unstated. The one-line description is insufficient for this complexity.

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 50%: 'serial' is documented in the schema while 'package' is not. The description partially compensates by clarifying that 'package' means the Android package identifier rather than a display name, but it adds no format examples or constraints, so it is only baseline-plus.

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 states a specific verb and resource ('Launch an app') plus the identifier type ('by package name'), which clearly separates it from siblings like list_apps and current_app. It does not explicitly name those alternatives, but the action is unambiguous.

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?

There is no guidance on when to use this versus current_app or list_apps, and no stated preconditions such as the app needing to be installed or a device being connected. The agent must infer all usage context.

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