render_screenshot

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

With no annotations, the description carries the burden of behavioral disclosure. It does add useful traits: full-page captures, retina scale, dark mode, and cookie-banner blocking. However, it doesn't explain how the image is returned (binary, URL, base64), whether JavaScript executes, or any limitations/quirks. The phrase 'element selection' is also not directly backed by a schema parameter, creating mild ambiguity.

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 two sentences with no filler. The first sentence delivers the core purpose, and the second succinctly lists notable capabilities. The structure is front-loaded and every phrase 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?

Given the rich input schema (8 well-documented parameters) and the clear statement that the result is visual, the description is nearly complete. The main gaps are lack of explicit sibling routing and the slightly misleading 'element selection' phrase, since no parameter lets the agent choose a specific element to capture. An agent can still invoke the tool correctly using just the schema and the core description.

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 thoroughly documents every parameter. The description mostly restates capabilities already present in the schema (fullPage, retina, darkMode, hide) and adds 'cookie-banner blocking' which has no parameter, so it arouses some confusion. It doesn't supply meaningful new parameter-level detail beyond the schema, hence the baseline score of 3.

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 specific verb and resource: 'Render a web page to an image and return it visually — gives the calling agent eyes on any URL.' This unambiguously states the tool's core function and makes it easy to distinguish from siblings like render_pdf or extract_page. The term 'element selection' is slightly vague, but the main purpose is crystal clear.

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 implies usage by saying it gives the agent 'eyes on any URL,' so an agent can infer this is the go-to tool for visual inspection of a page. However, it never explicitly contrasts with alternatives like render_pdf, extract_page, or create_og_image, and it provides no 'when-not-to-use' guidance. The intended use case is clear but not differentiated from siblings.

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