Set description

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

Annotations already declare readOnlyHint=false and idempotentHint=true, so safety and retry semantics are covered. The description goes further with real behavioral facts: only one https link is allowed, an empty string clears the value, variables accept plain text only (no link), and library assets are read-only here. Editor support (Design; unverified FigJam, Slides) adds environment context beyond 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?

Front-loaded with the core action, then constraints, then rename routing, then editor support. Dense but each clause carries a distinct rule; only the editor-support sentence is arguably peripheral to the write operation, which keeps it just under 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?

No output schema exists, but the description covers the meaningful surface of a 6-parameter write tool: valid targets, allowed formats, link limits, clearing behavior, read-only cases, and tool routing. What it returns is not described, which is a minor gap given the write-only nature of the operation.

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, but the description adds constraints the schema omits: variables take plain text only with no link (relevant to both description and markdown), and the one-link maximum for documentationLink. It still largely restates the target types and clearing behavior already documented on the fields.

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 (write) plus the exact resource written (the description and documentation link shown in the assets panel and Dev Mode) and enumerates the applicable target types: component, component set, local style, local variable. It is immediately distinguishable from rename/update siblings because it names those tools explicitly for the rename case.

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?

Gives explicit routing: "A set's description is the one people see — put it there rather than on a variant," and directs rename intent to figma_rename_node, figma_update_style, or figma_set_variable_properties with the exact field. It also states when the tool is unavailable (library assets are read-only) and which editors are supported vs unverified.

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