capture_screen

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

With no annotations, the description must disclose behavioral traits. It covers permission and target types, but omits details like output format (e.g., base64, file path), error handling, or what happens when invalid parameters are provided.

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?

Two sentences deliver the core purpose and a critical prerequisite (permission). No redundant phrases, front-loaded with main action.

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?

No output schema exists, so description should explain return format. 'Return it as an image' is vague. Lacks details on output type (e.g., base64 string, file path) and potential side effects. Adequate for a simple screen capture but not fully complete.

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% so baseline is 3. Description adds value by summarizing target enum and noting scale default 0.5. However, the region parameter's coordinate system (units) is not explained, and nested object constraints are implicit.

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?

Description clearly states 'Capture a screenshot of the macOS screen and return it as an image.' and lists three capture modes (full, region, frontmost), which distinctly separates it from sibling tools like get_browser_content or get_desktop_state.

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?

Mentions the required Screen Recording permission, which is a key prerequisite. It does not explicitly state when not to use, but the purpose is sufficiently distinct from siblings to infer appropriate contexts.

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