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

Annotations already cover the safety profile (readOnly, non-destructive, open-world), yet the description adds genuinely useful operational detail: quota consumption per screenshot, free cache/failed renders, the 6 MB threshold that switches to a download link, and that link's ~1-day validity. It stops short of stating auth requirements or rate limits.

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, front-loaded with the core action and output types, then quota, format preference, and size handling. No sentence is redundant and each carries distinct information.

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 13-parameter tool with full schema coverage and no output schema, the description covers the key runtime facts an agent needs (cost, size cap, format choice, download fallback). It leaves auth/permission expectations for private pages and any rate limiting unstated.

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 100%, so the baseline is 3, but the description adds a tradeoff not present in the schema: jpeg/webp keep the image small. That gives the agent selection logic for the format enum beyond the schema's mechanical enumeration.

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 and resource ('Render a public web page') and enumerates the output modes (image, PDF, scrolling video), which immediately distinguishes it from the only sibling, list_devices. The 'public' qualifier also frames the scope precisely.

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?

Offers concrete guidance: prefer jpeg or webp for smaller images, and the note that cache hits and failed renders don't consume quota helps the agent reason about retries. The 'public web page' wording implicitly excludes authenticated pages, but there is no explicit when-not statement or routing to alternatives.

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