Set Blend Mode

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

Beyond the annotations (readOnlyHint=false, idempotentHint=false), the description discloses meaningful mechanism: the mode is applied via the clip's Opacity effect and read back from stored state, and Premiere encodes it as an alphabetical index with Subtract/Divide appended. That index-ordering caveat is real behavioral context an agent could not infer. It still omits reversibility/permission details, so it is not a 5.

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 tight sentences with the purpose front-loaded before the technical addendum. The version-specific parenthetical ("mapped on Premiere 25.2.3 by rendering every index over a known background") is niche detail that borders on trivia but does document a real caveat.

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?

An output schema exists, so return values need no explanation, and both parameters are fully schema-documented. The description adds the mechanism and index caveat, giving an agent enough to call it correctly, though prerequisites (e.g. the clip needing an Opacity effect) remain unstated.

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% with a full enum, so the baseline is 3; the description earns above that by explaining why the enum maps to backend indices (alphabetical ordering, Subtract/Divide last), which clarifies the blend_mode parameter's semantics. node_id is left entirely 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?

States a specific verb and resource ("Set a video clip's blend mode") plus the implementation path ("through its Opacity effect"), so an agent knows exactly what changes. It does not explicitly distinguish itself from near neighbors like set_clip_opacity or set_frame_blend, which share the same territory.

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 never says when to reach for this tool versus set_clip_opacity, set_frame_blend, or manual effect manipulation, and gives no prerequisites or exclusions. Usage is only implied by the phrase "Set a video clip's blend mode."

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