open_app

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

Without annotations, the description carries the burden of disclosing behavior. It does add value by specifying 'or brings to front', indicating behavior when the app is already running. However, it does not mention error conditions, permissions, or what happens when the app name is invalid, leaving some gaps.

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 that conveys the action, resource, and examples without any filler. Every word earns its place, making it highly efficient.

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 one-parameter tool with no output schema, the description covers the core behavior (launch/focus) and provides examples. It lacks mention of error handling or prerequisite actions like listing apps, but the tool is simple enough that this is acceptable.

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 100% with a clear appName description, but the tool description adds concrete examples (Safari, Mail, Terminal, Spotify) that clarify what constitutes a valid app name. This goes beyond the schema and helps resolve ambiguity.

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 a specific action ('Launches or brings to front') on a specific resource ('a macOS application by name'), with concrete examples (Safari, Mail). This directly distinguishes it from sibling tools like quit_app (opposite action) and list_apps (different purpose).

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 implies usage context: use this when you need to open or focus a macOS app by its name. However, it does not explicitly state when not to use it or mention alternative tools like list_apps for discovering names, so guidance is only implicit.

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