viewport_screenshot

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

With no annotations, the description carries the burden of behavior disclosure. It states that it writes a PNG file and returns the absolute path, which is useful. However, it does not mention potential side effects, failure conditions, or whether the viewport is altered, leaving some gaps for a file-writing operation.

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 a single, front-loaded sentence that conveys both the action and the key return value. Every word earns its place, with no extraneous detail.

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 relatively simple screenshot tool with rich schema documentation and no output schema, the description covers the essential points: what it captures and what it returns. It could add niche details like coordinate spaces or error behavior, but these are not critical for this tool's use case.

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 each parameter (show_ui, filename, resolution) is already well-documented in the schema. The description adds no additional parameter semantics beyond what is provided, so the baseline score of 3 applies.

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 uses a specific verb ('Capture') and resource ('active viewport') and specifies the output format ('PNG file'). It clearly distinguishes from sibling viewport tools like viewport_camera or viewport_mode by focusing on screenshot capture.

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 clearly implies when to use the tool: when a screenshot of the viewport is needed, especially for visual inspection. It mentions returning a filesystem path for Claude Code to read, providing context for usage. However, it does not explicitly mention alternatives or exclusions, so it falls short of a 5.

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