Screenshot the viewport

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

With no annotations, the description carries the full burden and does well: it discloses the on-disk side effect (writes a PNG), the return value (path, plus optional data URL), and transparency compositing behavior. It omits any failure/error behavior, but coverage of the core traits is strong.

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?

Four tight sentences, front-loaded with what the tool does and why it exists. Minor redundancy with the schema on background, but essentially no wasted prose.

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 6-parameter, no-annotation tool, the description covers the main behavior, output, and two key flags, but leaves width/height unexplained and says nothing about limitations or failures. Adequate, 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 only 33%, so the description must compensate. It usefully explains crop semantics (auto-crop vs full viewport) and include_data_url, but width and height are undocumented in both schema and description, and the background explanation largely repeats the schema text.

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+effect: render the preview to a PNG on disk and return the path. No sibling performs screenshots, so it is unambiguously distinguishable from the surrounding tools.

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?

"This is how an agent looks at its own work" gives a clear purpose/context for reaching for this tool, and it explains the crop=true default choice vs crop=false and the background override. It stops short of naming explicit alternatives or when-not-to-use conditions.

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