figma_set_instance_properties

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

With no annotations, the description carries the full burden and does well: it discloses that direct text node editing 'may fail silently,' that the #nodeId suffix pattern is handled automatically, and that a Desktop Bridge connection is required. It stops short of describing what the response looks like or how partial/invalid property keys are handled.

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?

Purpose is front-loaded, followed by a clearly flagged IMPORTANT block and the exclusion. Dense but nearly every sentence adds a distinct constraint; the property-type sentence slightly overlaps the schema text.

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 2-parameter mutation tool with no annotations and no output schema, the description covers prerequisites (Desktop Bridge), failure modes, and scope limits. Only the return value and error behavior for invalid property keys are left unaddressed.

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 adds value by enumerating the property kinds (TEXT, BOOLEAN, INSTANCE_SWAP, VARIANT) and their value types, and by clarifying that SLOT properties are out of scope. That meaningfully extends the schema's generic key/value 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?

States a specific verb and resource: 'Update component properties on a component instance.' It also implicitly distinguishes itself from figma_set_text by warning against direct text node editing, and from figma_append_to_slot by naming the SLOT exclusion.

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?

Explicitly says to use this tool instead of editing text nodes directly when working with component instances, and names the correct alternative (figma_append_to_slot) for SLOT properties. Both the when and the when-not are stated with a named sibling.

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