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

Annotations already declare a safe read-only, non-destructive operation. The description adds real behavioral context beyond that: rendering is desktop width only, uses the live page's rules, and excludes web fonts and remote pictures. It stops short of describing the return artifact (image vs. HTML), which would matter most for a view tool.

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?

Front-loaded with the core action, then usage timing, then a concrete inspection checklist. Three sentences with no filler, though the 'look for' list is slightly long relative to the rest.

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 saying what comes back, and it never states the return format (screenshot, image URL, or markup). It covers rendering rules and the inspection intent well, but leaves that output-shape gap and the undocumented interfaceId for an agent to guess.

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 50%, so the description is expected to compensate, and it says nothing about either parameter. interfaceId is left entirely undocumented and workspace constraints are not restated from the schema. The 50% gap is not closed by the prose.

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 (see/look at) and resource (a Napkin interface), and immediately distinguishes itself from reading code by contrasting render versus source. The sibling set includes interfaces_get/write/list/get, and 'see what an interface LOOKS like right now' clearly separates this render/view tool from those.

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 timing guidance: 'Use it after every write and before saying an interface is finished.' That is a clear when-to-use rule. It does not name sibling alternatives (e.g., interfaces_get for metadata) or state when not to use it, so it falls short of a 5.

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