Screenshot

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

With no annotations, the description carries the full burden and does disclose key behaviors: a real headless-browser render, base64 return encoding, and the capture modes (custom viewport, full-page, waiting for a selector, cookie-banner dismissal). However, it omits failure behavior, timeout/resource cost of full-page capture, and the potentially very large size of the base64 output — gaps an agent would benefit from knowing.

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 with zero filler: the first states the action and return format, the second enumerates the distinguishing capabilities. The core verb is front-loaded, and every clause 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?

For an 8-parameter tool with no output schema, the description compensates well by stating the return encoding (base64 PNG/JPEG) and the main feature flags, while the schema covers parameter details. The only meaningful gap is the absence of selection guidance against the fetch/extraction siblings.

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 the schema already documents all 8 parameters. The description echoes them in prose ('custom viewport size, full-page capture, waiting for a CSS selector, dismissing cookie consent banners') without adding format, constraint, or interaction details beyond what the schema provides. Baseline 3 is appropriate.

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 states a specific verb and resource ('Capture a screenshot of a web page using a headless browser') and specifies the return format (base64 PNG/JPEG). None of the 29 sibling tools capture visual output — they fetch, extract, audit, and parse — so the tool is instantly distinguishable without inspecting the schema.

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 second sentence implies when this tool is appropriate (when rendered visual evidence is needed, with options like full-page capture and waiting for a selector), but it never explicitly names alternatives or conditions for choosing screenshot over fetch_page or extract_content. Usage context is implied rather than stated.

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