check_app_installed

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

Beyond the readOnly/non-destructive annotations, it discloses three non-obvious traits: detection is macOS-only with other platforms always reporting not installed, the result is stable within a session so caching is safe, and the return is a prose sentence plus a JSON object with named keys.

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?

Three sentences, front-loaded with the core purpose, then output shape, then the platform caveat and decision rule. No filler and every clause carries actionable information.

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?

With no output schema, the description compensates by naming the return shape (sentence plus { installed, paths, platform }), and it supplies the decision context the agent needs. Nothing required to call it correctly is missing.

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?

This tool takes zero parameters, so there is nothing to document and the baseline is 4. The mention of `filePath` refers to open_in_app's parameter, not this tool's, so it neither helps nor hurts.

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 states a specific verb and resource ('Check whether the Diagrammo desktop app is installed') and immediately distinguishes itself from sibling tools like open_in_app and share_diagram by naming them as the consumers of its result.

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?

It gives explicit when-to-use guidance ('one call is enough before deciding how to show a diagram') and a complete decision rule: installed → open_in_app with `filePath`, otherwise → share_diagram. When-not-to-use is implied by the session-stable note, which tells the agent not to call repeatedly.

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