open_app

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

No annotations are provided, so the description carries the full burden. The 'installed' qualifier does hint at a precondition (it will fail on uninstalled apps), but the description says nothing about foregrounding behavior, permission prompts, or failure modes.

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?

One short front-loaded sentence with the accepted input forms grouped inline as an example. Nothing is wasted and nothing essential 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 one-parameter tool this is close to sufficient, but with no output schema an agent cannot learn what a successful call returns or how failure (app not installed) surfaces. A clause covering that would complete it.

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% and the schema already states 'App name or package', so the description only adds the concrete example 'Messenger'. That helps but is marginal against a fully documented single parameter, so the baseline 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 clear verb+resource ('Open an installed app') with two accepted identifier forms, and the word 'installed' implicitly separates it from install_apk and list_apps. It never names a sibling explicitly, so differentiation is inferential rather than stated.

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?

Usage is implied by the verb — launch something already on the device — but there is no explicit when-to-use, no pointer to list_apps for discovering names, and no statement of what to do when install_apk is the right prior step.

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