Create variable collection

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

Annotations already declare the safety profile (readOnly=false, destructive=false, idempotent=true), yet the description adds genuinely non-derivable behavior: the first mode is named after modes[0] or "Default" and never Figma's "Mode 1," extra modes are paid-plan gated, and a refused mode surfaces as a `warnings` entry rather than a silent drop. With no output schema, disclosing that warnings channel is especially valuable for an agent interpreting results.

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?

Roughly four dense sentences, all carrying usable facts, with the resource named up front. The em-dash asides and the "Mode 1" trivia are slightly conversational but earn their place by preventing a real naming mistake; the missing leading verb is the only structural blemish.

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 create tool with no output schema, the description covers naming behavior, plan limits, failure signaling, follow-up editing, and environment support. It only partially addresses what a successful result looks like (it references "the result" and `warnings` but never says a collection is returned/identified), which is a minor gap.

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 75%, so the schema already carries most parameter meaning (notably the idempotencyKey retry semantics). The description adds real interpretation of `modes` beyond its schema text — the default naming rule and the "Mode 1" pitfall — though it says nothing extra about `session` or `idempotencyKey`.

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 opening identifies the artifact created — "A new variable collection" — and glosses it helpfully as "a token group," so an agent knows this is a creation tool for a Figma variable collection rather than a variable itself. It does not open with an explicit verb ("Creates"), and it only loosely distinguishes itself from siblings by pointing to figma_update_variable_collection.

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 routes the agent for follow-up work ("Rename or remove modes later with figma_update_variable_collection") and states environment scope ("Editors: Design; unverified: FigJam, Slides"). There is no explicit when-not or prerequisite statement, but the alternative and the plan constraint are named.

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