open_appLaunch a macOS app or raise its running window to the front; optionally capture a fresh screenshot of the front window to verify the result.
Open an app, or bring it to the front if it's running, e.g. "Xcode", "Slack", "Simulator", "Android Studio", "Figma".
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | ||
| look_after | No | Return a fresh screenshot of the front window after the action, to check the result |
Changes observed during successful MCP inspections.
v0.11.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden. It usefully discloses that a running app is brought to the front rather than duplicated, which is real behavioral value. However, it omits what happens if the app is not installed, whether a screenshot/return value is produced, and any permission requirements.
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 the core behavior first and examples last. Every clause earns its place; nothing is padded.
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 two-parameter tool with no output schema and no annotations, the description covers the essential launch-or-focus semantics. The main missing piece is failure behavior when the named app is absent, which is a modest gap rather than a blocking one.
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%: 'look_after' is documented in the schema, while 'name' has no schema description. The examples ('Xcode', 'Slack') do clarify that 'name' expects an app name string, partially compensating. This lands at the baseline for a half-documented schema.
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+resource ('Open an app') and clarifies the dual behavior (launch vs. bring to front), which is genuinely distinguishing. Concrete examples ('Xcode', 'Slack', 'Simulator') remove ambiguity about what counts as an app. It does not explicitly contrast with the sibling open_url or browser_open, so it falls short of a 5.
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 through its phrasing but never states when to use this over alternatives like open_url, browser_open, or browser_navigate. An agent must infer the app-vs-URL split from the tool name alone. Adequate but with a clear routing gap.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.