Add a keyframe to an effect property at a specific time to animate property values within a clip.
Add a keyframe to an effect property at a specific time
| Name | Required | Description | Default |
|---|---|---|---|
| time | Yes | Time in seconds (relative to clip start) | |
| value | Yes | Value at this keyframe | |
| clipIndex | Yes | Clip index | |
| trackType | Yes | Track type | |
| trackIndex | Yes | Track index | |
| effectIndex | Yes | Effect/component index | |
| propertyName | Yes | Property display name |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. It implies a mutation but does not disclose whether an existing keyframe at the same time is overwritten, what the default interpolation is, what permissions are required, or what happens if the property is not keyframable.
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 description is a single front-loaded sentence with no wasted words. It states the core action and scope immediately, though the resulting brevity leaves behavioral gaps that are better assessed under contextual completeness.
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 seven-parameter mutation tool with no annotations and no output schema, the description is too thin. It does not explain keyframe replacement behavior, interpolation defaults, error conditions, or what the tool returns, leaving the agent without enough context to call it confidently.
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 seven parameters, including time units and track type enum. The description only restates the idea of a specific time and adds no syntax or meaning beyond the schema, making the baseline 3 appropriate.
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?
The description uses a specific verb and resource: it adds a keyframe to an effect property at a given time. This clearly distinguishes it from add_audio_keyframe, but it does not explicitly name or differentiate against siblings like get_keyframes, remove_keyframe, or set_keyframe_interpolation.
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?
There is no guidance on when to use this tool versus alternatives such as add_audio_keyframe, set_effect_property, or set_keyframe_interpolation. It also omits prerequisites, such as whether the effect property must already exist or be keyframable.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.