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

Annotations already establish the safety profile (not read-only, not destructive, closed-world), so the description correctly spends its budget elsewhere: it discloses that invalid token values are refused and that the caller is told which one failed. It does not say whether changes apply to a draft or go live immediately, which for a theme mutation would be useful.

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?

Four sentences, zero filler, front-loaded with the action and then escalating into the prerequisite and value-format rules. Every sentence changes how the agent would call the tool.

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 no output schema and zero schema description coverage on a nested-object parameter, the description supplies exactly the missing pieces: key provenance, accepted value formats, and error behaviour. The remaining omission (the meaning of 'note') is minor.

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 0% and tokens is a free-form nested object, so the description must carry the semantics — and it does, specifying hex/rgb() for colours, unit-bearing lengths, and width/height or 'auto' for imageRatioCard/imageRatioProduct. Only the optional 'note' parameter goes unexplained.

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 ('Change the shop's colours, fonts or shape') and names get_theme_tokens as the source of valid keys, which sharpens what the tool operates on. It does not distinguish itself from the closely-named sibling set_theme_settings, so an agent must infer the split.

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 an explicit prerequisite and prerequisite ordering: keys come from get_theme_tokens and the agent should 'call it first'. That is real routing guidance. It stops short of stating when-not to use this versus set_theme_settings or branding_set.

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