ui_screenshot

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

No annotations exist, so the description carries the full burden. It discloses the locator precedence, iframe priority, top-level coordinate semantics, and the exact result fields (base64, crop box, frame, locator source, hash). This is strong transparency, although it omits behavior around size limits or timeouts.

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 compact sentences, each carrying useful information; the main purpose is front-loaded and technical details follow in a logical order. No filler.

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 an 18-parameter tool with no annotations, the description covers the central selection logic and result shape, but it under-documents several input parameters and the interaction with siblings. The output schema presumably covers return values, so some completeness is recovered.

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 has 0% description coverage, so the description must compensate. It explains the core locator parameters (css, role, name, description, xpath, text, placeholder) and the x/y/width/height rectangle fallback, but it leaves many parameters (image_format, quality, max_bytes, padding, timeout_ms, in_iframe) undescribed.

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 opens with a clear verb and scope: capturing a DOM element or top-level viewport region and returning a resized image. It also outlines the locator fallback order, but it does not explicitly differentiate from sibling tools like ui_snapshot, so 4.

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 explains how element locators work and when to fall back to x/y/width/height, but it never states when to choose this tool over related siblings (e.g., ui_snapshot, overlay_scan). No explicit alternatives or exclusions are provided.

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