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

Annotations already declare openWorldHint=true, destructiveHint=false and readOnlyHint=false, so the bar is lower; the description still adds real context — headless Chrome execution, the import-vs-return side effect depending on `project`, and that reduced motion is requested by default so stills don't catch transitions. It does not cover timing, failure behavior on unreachable pages, or rate limits, which keeps it off a 5.

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?

Three sentences, front-loaded with the core action and modes, then output routing, then the scroll alternative. Every clause carries information (scope, side effect, or constraint) with no filler or restatement of the tool name.

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?

With 13 parameters, no output schema, and an open-world fetch, the description does the important work: it discloses where the artifact ends up (project import vs returned result), which is the only return-value information an agent gets. It leaves out what the returned image payload looks like and what happens on capture failure, a modest but real 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?

Schema coverage is 100%, so the baseline is 3; the description earns above that by documenting cross-parameter relationships the schema states only in isolated property descriptions — scroll produces a project import, conflicts with fullPage/selector, and overrides the view to 1440x810 unless width/height say otherwise. It does not restate defaults like scale=2 or theme semantics, which the schema already handles.

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 opening sentence names a specific verb and resource (screenshot a web page in headless Chrome) and immediately enumerates the three capture modes: first screen, full page, one element. The follow-up sentences add the routing outcome (into a project vs returned in the result) and the scroll/video variant, so an agent can distinguish all modes without opening the schema.

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?

Explicit conditions and exclusions are given: scroll 'Needs project; not with fullPage or selector', and without a project the image 'comes back in the result'. It even explains the choice between scroll and full page (sticky headers stay in view vs one tall still the edit has to pan over), which is exactly the kind of decision guidance that selects a mode.

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