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

Strong disclosure beyond the annotations: public values persist immediately, secrets are never accepted in chat and instead create a placeholder plus a paste link. That is exactly the kind of auth/side-effect context annotations can't convey. The one gap is that destructiveHint=true is never explained — nothing says whether setting an existing variable name overwrites or errors, which matters for a mutation tool.

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, each carrying distinct information, with the primary trigger front-loaded and the secret-handling rule following immediately. No restatement of the name or title, no filler.

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?

Complete for a 3-param mutation with no output schema: it covers the trigger, the secret flow, the return value (the paste link), and the sibling alternative. The only omission is overwrite behavior for an existing variable name, which is a meaningful unknown given destructiveHint=true.

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 67%, with name and value documented but site_id bare. The description compensates by supplying the conditional rule the schema can't express ('leave value out' for secrets, only populate it for NEXT_PUBLIC_ variables), which is the critical decision point for this tool. It does not explain site_id, leaving that param unqualified in both places.

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 first sentence names the specific verb+resource ('set an environment variable on one of the user's WebTwizz sites') and immediately distinguishes the three value paths: public, secret, and connector-managed. An agent can tell this apart from list-connectors/use-connector without opening any 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?

Explicit when-to-use ('when one of the user's sites needs an environment variable') and explicit when-not-to-use with the named alternative ('services WebTwizz connects, like Stripe, Supabase or Resend, get their keys through list-connectors and use-connector instead'). It also states the prerequisite behavior for secrets (leave value out).

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