List library variables

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

Beyond the readOnlyHint/destructiveHint/openWorldHint annotations, it adds real behavioral context: an explicit 'Reads only.' restatement for emphasis, a named permission dependency (teamlibrary), a defined error state (UNSUPPORTED) with causes and remediation, and per-editor support status (Design verified; FigJam/Slides unverified).

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, dense, and free of filler — nearly every clause carries a distinct fact (scope boundary, mode split, return shapes, filters, import rule, sibling, error state, editor support). The em-dash-packed single paragraph is efficient but harder to skim than a short bulleted split would be.

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?

With no output schema, the description carries the full burden of describing returns, and it does: { key, name, libraryName } for collections and { key, name, resolvedType } for variables, plus truncation/cursor behavior. Nothing an agent needs to call this correctly is missing.

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 83%, so the baseline is 3, and the description still clarifies the highest-risk semantic: collectionKey switches the entire result shape and paging behavior between collections and variables. It also explains that `query` matches name or library name on collections and that results are paginated. The remaining params (limit, cursor, session) are left to the schema.

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?

Starts with a specific verb+resource (variables from team libraries enabled in this file) and immediately scopes it against the rest of a library ('its components and styles it cannot'). It is unambiguously distinguishable from figma_get_variable_defs, which it explicitly names as the local-variables counterpart.

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?

States the two operating modes (without collectionKey vs. with one), routes local-variable lookups to figma_get_variable_defs, explains the import-before-bind prerequisite, and defines the UNSUPPORTED condition with its likely causes (missing teamlibrary permission or no library enabled, with the Assets → Libraries remedy). When/why-not coverage is essentially complete.

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