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 clearly states the operation is a screenshot with real-browser rendering and returns a PNG image, which is useful. However, it does not disclose potential side effects (e.g., it's a read-only action), rate limits, or failures (e.g., page not loading).

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 three sentences, each earning its place: what it does, when to use it, and what it returns. It is front-loaded with the primary action and scoped with use-case examples. No wasted words.

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?

The description is complete for selecting and invoking the tool: it explains behavior, return type, and typical use cases. It lacks explicit error handling or edge cases, but given the straightforward parameter set and no output schema, this is a minor gap.

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?

The input schema has 100% coverage with detailed descriptions for all four parameters (url, width, height, full_page). The description does not add new semantic meaning beyond the schema, but since schema coverage is high, a baseline of 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 uses the specific verb 'Take a screenshot' with a clear resource ('a web page as it actually renders in a real browser, after JavaScript has run'), and unlike siblings (rendered_html, url_to_pdf), it explicitly focuses on visual rendering and returns a PNG. This differentiates it from alternatives without needing to inspect them.

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 provides clear context: 'when you need to see a page rather than read it' and gives concrete use cases (checking a layout, confirming a site is up, capturing what a user would see). It does not explicitly mention when not to use it or alternatives, but the context is strong enough for an agent to decide.

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