Set blend mode

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

Adds context beyond the annotations: per-item result shape, the guarantee that a single node failing does not fail the call, and editor/platform support (Design vs unverified FigJam/Slides). Annotations already cover the idempotency/safety profile, so this is meaningful extra disclosure, though it doesn't address permissions or reversibility.

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-loads the core action, then scoping, then alternative, then return contract, then platform support. Dense with zero filler sentences, though the return-shape notation is slightly heavier than needed inline.

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 correctly supplies the return shape and partial-failure behavior, and adds editor compatibility. A mutation tool of this complexity could still note required permissions or what happens to nodes whose blend mode is invalid, but coverage is strong.

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?

With 75% schema coverage the baseline is 3, and the description earns above that by clarifying that PASS_THROUGH is limited to frames and groups, adding a semantic constraint on blendMode not present in the enum. nodeIds/session/idempotencyKey semantics remain carried by 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?

States a specific verb+resource ('set how nodes blend') and it maps directly to the tool name. It explicitly distinguishes itself from the sibling figma_set_opacity by routing transparency work there, so an agent can tell the two apart without opening a schema.

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?

Names the alternative (figma_set_opacity) and the condition that selects it, and notes PASS_THROUGH applies to frames/groups only. There are no explicit when-not-to-use exclusions beyond that one routing hint, so it stops just short of 5.

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