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

No annotations are provided, so the description carries the full behavioral burden. It does disclose meaningful traits – that visible styles must live in the html, that backgroundColor/borderRadius only affect plain boxes, and that a <style> element stays scoped inside the card – but says nothing about mutation semantics, reversibility, or limits on the resulting layer, leaving real gaps for a write operation.

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 tightly packed sentences with no filler, front-loaded with the core action and then the customization mode. The one weak spot is a slightly abrupt trailing clause about the style element, but overall it reads efficiently.

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 14-parameter mutation tool with no output schema and only 71% schema coverage, the description covers the central html workflow well but omits orientation info (opacity, rotations) and any return/result expectations. It is adequate but not complete.

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 71%, so most parameters are already documented in the schema, and the description adds useful context about how width/height define the layout box and how they interact with html. It adds nothing for the undocumented parameters (opacity, borderRadius, backgroundColor, screenshotId), so it only marginally compensates for the coverage gap.

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 description states a specific verb and resource: 'Add a box layer to a card,' and the html sentence clarifies it is the freeform-HTML card primitive. It implicitly separates itself from add_text/add_phone (text/phone layers) but never names those siblings outright, 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?

It gives conditional guidance for two modes – pass html to draw a custom card, or omit it for a plain box styled by backgroundColor/borderRadius – which implies when each path applies. However, it never names an alternative tool or states when to prefer add_div over add_text, add_screenshot, or update_div, leaving routing to inference.

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