Adds or updates a keyframe on a node knob at a specified frame, creating animation if the knob is not already animated.
Set a keyframe on a knob at a specific frame. Creates animation if the knob is not already animated.
Args: node: node name. knob: knob name. frame: frame number. value: value at that frame.
| Name | Required | Description | Default |
|---|---|---|---|
| knob | Yes | knob name. | |
| node | Yes | node name. | |
| frame | Yes | frame number. | |
| value | Yes | value at that frame. |
Changes observed during successful MCP inspections.
v0.2.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare idempotentHint=true and destructiveHint=false (safe, repeatable), and the description usefully adds that missing animation tracks are created automatically. However it is silent on what happens when a keyframe already exists at the frame (overwrite vs add) and on value units, which matters for a mutation tool.
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 first sentence is well front-loaded and does real work, but it is followed by an Args block that duplicates the input schema word-for-word, adding length without value.
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 4-required-param mutation with no output schema and annotations covering the safety profile, the description is adequate but leaves out overwrite semantics, value units, and error behavior when node/knob are invalid.
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 description coverage is 100%, so the schema already documents all four parameters. The Args block merely restates those descriptions verbatim ('node: node name.', 'value: value at that frame.') with zero added meaning, so baseline 3 applies.
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 a keyframe on a knob') and adds the meaningful side effect that animation is created if absent. It is implicitly distinguishable from siblings like set_knob and list_keyframes, though it never names the alternative it supersedes.
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?
No guidance on when to use this versus set_knob, set_expression, or keyframe-editing siblings, and no prerequisites (e.g. that node/knob must already exist). The agent must infer usage from the name alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.