figma_set_variable_value

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

With no annotations, the description carries the burden of behavioral disclosure. It mentions 'Uses REST API' as a technical detail but does not disclose whether the operation overwrites existing values, requires specific permissions, or is reversible. A mutation tool with zero annotation coverage should provide more context.

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?

Two short sentences, front-loaded with the action, and every sentence adds useful information. No filler or repetition.

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 mutating tool with no annotations, no output schema, and a critical undocumented parameter ('value'), the description is insufficient. It does not explain return values, error handling, or the format of the value to set, leaving a significant gap in operational context.

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 75% (modeId, fileKey, variableId have descriptions), but the 'value' parameter—the core of the operation—lacks both schema and description-level explanation. The description helps with modeId by pointing to figma_get_variables, but leaves 'value' semantics unresolved.

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 clearly states the action ('Set variable value') and the specific scope ('for a mode'), making it distinct from sibling tools like figma_update_variable or figma_bind_variable. The wording is specific and actionable.

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?

Provides clear context: 'Uses REST API — no plugin required' tells the agent when this tool is appropriate (when plugining is not wanted), and 'Use mode ID (get from figma_get_variables)' gives a prerequisite. However, it does not explicitly list alternatives or exclusions.

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