open_in_preview

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

With no annotations, the description carries the burden of behavioral disclosure. It explains platform-specific behavior (Preview vs default viewer) and mentions annotation capability on macOS, but does not disclose side effects, return values, or environmental requirements. This is minimal but covers the key platform distinction.

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 exceptionally concise—two sentences with no filler. It front-loads the primary purpose and adds the platform detail in the second sentence. 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?

Given the tool's simplicity and the existence of an output schema, the description adequately covers the core behavior. It lacks details about return values or error handling, but those may be covered by the output schema. The platform-specific note adds valuable context, making it nearly complete for this tool type.

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 description coverage is 100%, so both parameters are documented in the schema. The tool description adds no extra meaning to the parameters, merely restating the action. Baseline 3 is appropriate since the schema handles parameter documentation and the description does not detract.

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 opens an image and specifies the target app (Preview on macOS). The phrase 'macOS only' is then contradicted by 'On other platforms, it opens with the default image viewer,' creating minor ambiguity about platform availability. It distinguishes from open_file_in_preview by focusing on images, but not explicitly.

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?

No guidance is provided on when to use this tool versus alternatives like open_file_in_preview or other image viewers. The description only explains the action, not the context or selection criteria. An agent receives no hints about appropriate use cases or exclusions.

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