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

Annotations already indicate this is a mutation, and the description adds important behavioral context beyond that: tokens are the single source of truth, and setting is_default=true atomically clears any existing default. This is a meaningful side-effect disclosure that helps an agent anticipate the consequences of the call.

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 description is three tight sentences with no filler. It front-loads the core action, then provides the critical token requirement and the notable default side effect. Every sentence contributes operational information.

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 create tool with five parameters, nested objects, and an output schema, the description covers the essential inputs and behaviors. A minor gap is that it does not explicitly acknowledge the optional title/subtitle overlays allowed by the schema, though the schema itself documents those, and the overlays comment is slightly ambiguous.

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?

The input schema already provides 100% parameter coverage with detailed descriptions, so the baseline applies. The description adds value by emphasizing that the tokens map must be complete, and by explaining the atomic default-clearing behavior of is_default. It also clarifies the role of cover_page and thank_you_page as selecting background images.

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 clearly states a specific action and resource: 'Create a new visual theme.' It further defines what a theme includes (tokens, cover-page and thank-you-page background images), making it easy to distinguish from siblings like update_theme, archive_theme, get_theme, and list_themes.

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 clear guidance on when to call this tool: when creating a new theme, providing a complete tokens map, and optionally setting it as the account default. It does not explicitly enumerate alternatives like 'use update_theme to modify an existing theme,' but the 'new' framing and sibling names supply adequate context.

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