Swap component

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

Annotations already declare idempotentHint=true and destructiveHint=false, lowering the bar. The description still adds real behavior: overrides are preserved 'where Figma can' (implying partial loss is possible), library components given by key are imported first, and editor support is scoped (Design; unverified FigJam/Slides). It does not state the failure modes when overrides cannot be mapped, which keeps it below a 5.

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?

Front-loaded with the operation, then alternatives, then environment constraints; every sentence carries information and none repeats the schema verbatim. It is a single dense paragraph rather than cleanly segmented lines, which is the only reason it is not a 5.

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 mutation tool with no output schema, it covers purpose, routing, prerequisite import behavior, and platform availability, while annotations cover idempotency and non-destructiveness. The idempotencyKey retry semantics live in the schema. It stops short of describing the result of a swap or partial-override-failure behavior.

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 description coverage is 100%, so the baseline is 3 and the schema already documents nodeId, variant, componentId/componentKey/componentSetKey, and idempotencyKey. The description adds only one genuine nuance beyond the schema — that omitting `variant` yields the set's default variant, and that keyed components are imported first. Useful but marginal against fully documented params.

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?

Precise verb+resource ('make an existing instance show a different component') with the exact mechanism spelled out, including the default-variant behavior for component sets. It explicitly distinguishes itself from figma_set_instance_properties and figma_create_instance by name, so an agent can route without opening a sibling 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 routing: 'To switch a variant of the SAME set, figma_set_instance_properties keeps the other values; to place a new instance use figma_create_instance.' The alternative and the condition selecting it are both stated, plus the library-import prerequisite for key-based swaps.

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