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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: rate limit (5 captures/min), depth/breadth caps (500 nodes, 10 deep), and the explicit note that it saves nothing. These are material operational facts not present in the annotations.

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 purpose and return-value enumeration are front-loaded and the workflow guidance comes before the caveats, so the structure is sound. It is dense but every enumerated item conveys concrete capability; the only slight cost is length, which borders on verbose even though each element earns its place.

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?

There is no output schema, so the description carries the burden of describing return values — and it does so thoroughly across all six artifact types. Combined with annotations covering the safety profile and rate limits, an agent has everything needed to call this correctly and interpret results.

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% and both parameters (url, viewport) are fully documented in the schema itself. The description does not add meaningful meaning beyond that — it does not mention the viewport parameter or its desktop/mobile options. Baseline 3 applies when the schema does the heavy lifting.

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+resource ('Capture a public URL for cloning') and immediately enumerates the six artifacts it returns, which differentiates it from siblings like screenshot_page, read_rendered_page, and read_rendered_page. An agent can distinguish it from those tools without opening a 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?

Provides an explicit workflow ('capture → study screenshot + element_tree → compose a fixture from primitives → call create_site_from_fixture') and names the alternative path for rehosting images (upload_image with url). It also states the condition for using this over the template path. Nothing is left to inference.

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