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

Beyond the annotations (readOnlyHint=false, destructiveHint=false), the description adds that the original is never modified, the copy starts unpublished, and — critically — "Each call makes another copy," warning that repeated invocations are not idempotent and will spawn duplicates. That is real behavioral value an agent cannot get from the structured fields.

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, front-loaded with the usage trigger, then outcome, then the repeat-call caveat. The dashboard analogy ("the way Duplicate does on the WebTwizz dashboard") is slightly decorative but cheap and orients the user.

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, the description never says what comes back — presumably the new site's id, which the agent would need for follow-up calls like edit-site or publish-site. It also doesn't say where the copy appears (drafts list?). The mutation and non-idempotency are covered, but the return-value gap is real.

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 50%: site_id has no description anywhere, and the description never states that it identifies the source site or what happens on an invalid id. The optional name parameter and its "<original name> (Copy)" default are documented only in the schema, so the description adds nothing on parameters.

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 names a specific verb and resource ("a copy of one of their WebTwizz sites") and spells out the outcome: a new, unpublished project with the same pages, design and content. That copy semantics implicitly separates it from create-site, though no sibling is named explicitly.

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?

"Use this when the user wants a copy of one of their WebTwizz sites, to try ideas without touching the original or to start a similar site" gives clear trigger conditions with intent. It stops short of an explicit when-not or a named alternative such as create-site for building from scratch.

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