open_app

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

No annotations are supplied, so the description carries the full behavioral burden, and it only covers the happy path. It says nothing about failure behavior for an invalid or uninstalled package, whether the app is brought to the foreground, or whether the call blocks until launch completes. For a simple, largely self-evident action tool this is adequate but clearly incomplete.

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?

Two short sentences, zero padding: the action and its argument format come first, and the alternative/derivation hint comes second in the natural reading order.

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, non-annotated action tool with no output schema, the definition covers purpose, argument format, and prerequisite discovery. The remaining gap is error/edge-case behavior, which matters but is minor given the tool's simplicity.

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?

The schema declares only an untyped string with 0% description coverage, so the description's reverse-DNS example is the sole source of format guidance and adds real value. It doesn't state whether the identifier is case-sensitive or what constitutes an invalid value, keeping it short of a 5.

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 specific verb ('Open') and resource ('an app'), scoped by package name, and includes a concrete example identifier (org.telegram.messenger). It also names the sibling used for discovery, so an agent can tell it apart from list_apps or open_url without opening any schema.

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?

Explicitly routes the agent to list_apps when the package name is unknown, which is the main prerequisite. It doesn't contrast against open_url (URLs vs. packages) or state what to do if the package isn't installed, but the primary when-to-use path is clear.

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