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Set Keyframe

set_keyframe

Create or update a keyframe on a Cinema 4D entity parameter for animation, supporting scalar and vector values with automatic track creation.

Instructions

Create or update a single keyframe on a resolved entity's parameter. Supports scalar (real/long/bool) and vector (x/y/z component) parameters; the bridge infers the dtype from the entity's description, or you can override it explicitly. Creates the CTrack automatically on first use.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
fpsNoTime base override (default: doc fps).
dtypeNoOverride the dtype when description lookup fails (rare).
frameYesFrame number.
valueYesValue at this frame (rotations in radians; bools coerce to 0/1).
handleYesEntity whose parameter gets the keyframe.
interpNoKey interpolation (default "spline").
param_idYesTop-level description id (e.g. c4d.ID_BASEOBJECT_REL_ROTATION = 904).
componentNoSub-component for Vector params. For C4D rotation (HPB) use "x" for H, "y" for P, "z" for B.

Schema Changelog

Changes observed during successful MCP inspections.

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    • addedInput schema / properties / value / type
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  2. Changed1 schema field changedv0.4.3
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      +        "const": "gv_node",
      +        "type": "string"
      +      },
      +      "name": {
      +        "type": "string"
      +      },
      +      "tag": {
      +        "allOf": [
      +          {
      +            "$ref": "#/definitions/__schema0"
      +          }
      +        ]
      +      }
      +    },
      +    "required": [
      +      "kind",
      +      "tag"
      +    ],
      +    "type": "object"
      +  },
      +  {
      +    "properties": {
      +      "kind": {
      +        "const": "plugin_options",
      +        "type": "string"
      +      },
      +      "plugin_id": {
      +        "anyOf": [
      +          {
      +            "maximum": 9007199254740991,
      +            "minimum": -9007199254740991,
      +            "type": "integer"
      +          },
      +          {
      +            "type": "string"
      +          }
      +        ]
      +      },
      +      "plugin_type": {
      +        "enum": [
      +          "command",
      +          "object",
      +          "tag",
      +          "material",
      +          "shader",
      +          "video_post",
      +          "scene_loader",
      +          "scene_saver",
      +          "bitmap_loader",
      +          "bitmap_saver",
      +          "tool",
      +          "preference",
      +          "node",
      +          "sculpt_brush"
      +        ],
      +        "type": "string"
      +      }
      +    },
      +    "required": [
      +      "kind",
      +      "plugin_id"
      +    ],
      +    "type": "object"
      +  }
      +]
  3. First observedv0.3.1

TDQS

A4.2/5.0
Behavior4/5

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

With no annotations, the description carries the burden and does disclose real behavioral traits: automatic CTrack creation on first use, dtype inference from the entity description with explicit override, and bool coercion to 0/1. It does not state whether an existing keyframe at that frame is overwritten vs merged, leaving a mutation-semantics gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three compact sentences, front-loaded with the action and scope, with no redundant restatement of schema fields. Every sentence adds functional information (scalar/vector support, dtype inference, auto track creation).

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For an 8-parameter mutation tool with no annotations and no output schema, the description covers the main behaviors an agent needs (what it mutates, dtype handling, side-effect of track creation). The main omission is what happens on collision with an existing keyframe at the same frame.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds meaning beyond the schema: it explains the dtype inference rule ('bridge infers the dtype from the entity's description, or you can override'), which contextualizes the dtype parameter rather than restating it.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource+scope: 'Create or update a single keyframe on a resolved entity's parameter.' The 'single' qualifier distinguishes it from batch-oriented siblings like set_params, and get_keyframes/delete_keyframe cover other keyframe operations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Implies usage context (scalar vs vector params, dtype inference on first use) but never explicitly says when to prefer this over set_params or batch, nor any preconditions such as an existing track. Usage is inferred rather than stated.

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