Bind a variable

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

Annotations already indicate readOnlyHint=false and destructiveHint=true, and the description adds a meaningful behavioral trait: the bound value will follow the token rather than remain a copy. It does not detail what gets destroyed by the binding, but the annotation already carries that destructive signal, so the description adds enough beyond the structured metadata.

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?

The description is two concise sentences with no filler. It front-loads the core behavior and then gives directly actionable field-value guidance. Every clause earns its place.

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?

All three required parameters are covered by the schema, and the description supplies the necessary semantic guidance for the free-form 'field' parameter. The main context not spelled out—destructive side effects and lack of output format—is already handled by annotations and the absence of an output schema on this mutation tool.

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 100%, so the baseline is 3, but the description enhances the 'field' parameter by pairing specific values with variable types (color vs. number) and adding useful numeric property examples. This goes beyond the schema's terse 'fill, stroke, or a numeric property' description.

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 states a specific verb ('binds'), a resource ('a variable from this file'), and a target ('a property'), while clearly distinguishing the behavior from setting a static value ('so the value follows the token rather than being a copy'). It effectively separates this tool from sibling tools like figma_set_fill or figma_set_stroke.

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?

The description gives concrete guidance on when to use which field values: 'fill' or 'stroke' for color variables, property names like cornerRadius or opacity for numbers. It does not explicitly name alternatives or exclusion conditions, but the 'rather than being a copy' phrasing provides clear context that this tool is for linking to tokens instead of setting independent values.

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