page_screenshot

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

With no annotations provided, the description carries the full burden and meets it: it discloses coordinate-space mapping to click/tap/drag tools, document-relative fullPage behavior with scrollY conversion, native pixel behavior of fullRes, element crop plus origin, and the expense of image content. No annotation contradiction exists.

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 dense but every sentence earns its place: core coordinate mapping first, then each option and its caveat, then the alternative tool and cost warning. No filler or repetition of schema text.

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?

Despite no output schema and no annotations, the description covers what an agent needs to call the tool correctly: what is captured, coordinate semantics for downstream actions, variant behavior, when not to use it, and a cheaper alternative. The only minor omission is a precise note on how the image is returned, which is not essential for invocation.

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 only 40%, so the description must compensate. It adds meaning beyond the schema for ref/selector (crop plus page origin), fullPage (document-relative and click-unsuitable), and fullRes (fine detail at native pixels). Only sessionId goes unmentioned, but it is a conventional session context parameter and not central to this tool's behavior.

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?

Opens with a specific verb and resource: 'Capture a PNG screenshot that is 1:1 with CSS pixels.' It then distinguishes the default viewport capture from fullPage, element, and fullRes variants, and explicitly contrasts with page_look for numbered click targets, so an agent can separate it from siblings.

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?

Gives explicit selection guidance: the default viewport is for reading coordinates to feed into page_click_at/page_tap_at/page_drag; fullPage should not be used for clicking and page_look/page_find is preferred; use sparingly due to cost. This is concrete and decision-ready.

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