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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so the bar is lower, yet the description adds real value: the return is an image, not structured data, and there is a CDN cache delay that can make results stale. Those are traits the annotations do not convey.

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?

Dense and front-loaded: purpose first, then per-parameter inline documentation using backticks, then a caveat. Every sentence earns its place, though the run-on formatting of the view/path examples is slightly cramped.

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 4-param, 0%-schema-coverage tool with no output schema, the description covers purpose, return type, viewport semantics, and cache behavior, but omits the `server` parameter entirely, which an agent may need to target the right host.

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 description coverage is 0%, so the description must carry the burden and it documents 3 of 4 parameters (path, view, site) with concrete examples and enum-like values. The `server` parameter is never mentioned, leaving a real gap at this coverage level.

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: 'Renders a page of the hosting site and returns a screenshot image.' An agent can distinguish this from site_fetch/site_read_file/site_info siblings without opening the schema. It does not explicitly name a sibling, so it stops short of a 5.

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?

Usage is implied by the flow context ('right after writing files... wait a few seconds and preview again') and by the 'leave it empty for the server's main website' instruction, but there is no explicit when-to-use statement or named alternative among the many site_* preview/read siblings.

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