start_app_activity

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

With no annotations, the description carries the full burden of behavioral disclosure. It adds useful context about the default launcher activity behavior, but it does not mention failure cases (e.g., app not installed), whether the call blocks, or any prerequisites. This is partial transparency.

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?

The description is concise: two sentences with no redundant information. It front-loads the core purpose and immediately follows with a useful behavioral detail. Every word earns its place.

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 simple launch tool with three well-documented parameters and no output schema, the description covers the essential function and the key nuance of default activity behavior. It could mention error handling or prerequisites, but the level of detail is appropriate for this 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?

The input schema already covers all parameters at 100% coverage, so the baseline is 3. The description adds value by explaining the optionality of activityName and what happens if it is omitted, which is not explicitly clear from the schema alone.

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 clearly states the tool's function with a specific verb and resource: 'Launch an app or a specific activity on the device.' This distinguishes it from sibling tools like install_app or force_stop_app, which serve different purposes.

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 provides clear context for when to use the tool (to launch an app or specific activity) and even mentions the fallback behavior when no activity is provided. However, it does not explicitly mention exclusions or alternative tools, so it stops short of a 5.

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