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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=false, so the safety profile is covered. The description adds genuine context: the starter theme is 'complete, installs as is', and it imposes an ordering dependency via get_design_guide. It stops short of stating that repeated calls create distinct themes or what is returned.

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 sentences, zero filler, and the default-source behavior plus the prerequisite are front-loaded before trailing detail. Every sentence earns its place.

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 three-parameter creation tool with no output schema, the description covers the essential default behavior and the mandatory precondition. It leaves minor gaps around naming semantics and post-creation result, but nothing that would cause a mis-invocation.

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 33% (only slug documented), so the description must compensate. It does communicate the effective default for `from` (reference starter theme unless a blank one is asked for), which is real added meaning, but says nothing about `name`, the other undocumented parameter.

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 and resource ('Start a theme of the merchant's own') and pins the default source ('from the starter theme ... unless asked for a blank one'). An agent can separate this from sibling write_own_theme_files or set_theme_settings without opening a schema.

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?

Explicitly names the selecting condition ('when the merchant wants a design from scratch rather than changes to the theme they wear') and the alternative it is not, plus a required prerequisite ('Call get_design_guide first'). This is exactly the when/when-not/alternative structure.

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