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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety bar is pre-cleared. The description adds real behavioral context beyond that: no models or images to load, the scene is generated client-side, embedding is free but requires a visible credit line, and the output contains multiple embed forms. That licence/attribution constraint is the kind of detail an agent would otherwise miss.

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 deliverable and structured as output-then-inputs, with no wasted preamble. The long flower and scene-variant enumeration is decorative relative to the season enum, but it still maps to real parameter values, so the cost is small.

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?

With 6 optional parameters, nested objects, and no output schema, the description carries the return-shape burden and does so by naming the element, iframe, link and licence line. Combined with the sourcing rule for roles/colors and the free-with-credit note, an agent has enough to invoke 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 description coverage is 100%, so the baseline is 3. The description explains the roles-vs-colors-vs-palette selection strategy and their provenance from decode_url, but the key precedence rules ('palette wins over roles', 'colors used when roles alone hold fewer than three strong colours') are already stated in the schema, so it adds only marginal meaning.

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 precise verb and artifact ('Returns paste-ready code for a CSS Crème Scene') and enumerates exactly what comes back: the <creme-scene> element, an iframe, a full-screen link and the licence line. It also distinguishes itself from the decode_url sibling by explicitly noting 'It reads no URL itself', so an agent can route between them without opening schemas.

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 a clear workflow: feed it the `roles` (and optionally `colors`) from a decode_url result, or pass a `palette` of hex values, which tells the agent when this tool is the right next step after decode_url. It stops short of naming exclusions or when-not-to-use cases, so it is clear context rather than full routing guidance.

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