Capture a screenshot

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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely non-obvious behavior: cookie banners and ad overlays are removed by default (the captured page is not raw), each call costs 1 credit, and return_image=false keeps large captures out of the context window. It stops short of disclosing auth/crawl restrictions or failure modes for unreachable URLs.

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 short sentences: purpose first, default side effect second, cost third, parameter tips last. Nothing is repeated verbatim from the schema and each sentence changes what the agent would do.

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 open-world tool with no output schema, the description covers the essentials an agent needs: what comes back (an image), the credit cost, the default cleanup behavior, and the context-window escape hatch. The two viewport parameters remain unexplained anywhere, which is the only notable hole.

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 63%, and the schema already documents delay, format, full_page, and return_image well. The description adds real value for `device`, whose enum has no schema description, by explaining it emulates a phone or tablet, but viewport_width/height and format go unmentioned in prose, leaving the description roughly at baseline.

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?

"Render a URL in a real browser and return the image" is a specific verb + resource + output, and the phrase "so you can see the page" frames the agent-facing benefit. It implicitly separates itself from capture_pdf and audit_accessibility by promising an image, but never names the sibling tools the way a 5 would.

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 tells the agent how to use two parameters (full_page, device) but never says when to pick this over compare_pages, capture_pdf, or audit_accessibility, nor when not to call it (e.g. pages requiring auth or JS-heavy SPAs). Usage is implied by the parameter tips rather than stated as selection criteria.

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