Arkeonix CapCut MCP

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capcut_add_audio

Add an audio clip to a CapCut draft at a chosen timeline position on a selected track or a newly created one. Use it to place voiceovers, music, or sound effects in video projects.

Instructions

Add an audio clip at a time on a track.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "draft": "<draft>",
      "file": "<file>",
      "atSec": "<atSec>"
    },
    "name": "capcut_add_audio"
  }
}

Input Schema

Name	Required	Description
`file`	Yes
`posX`	No
`posY`	No
`atSec`	Yes	start time on the timeline, seconds
`draft`	Yes
`scale`	No
`speed`	No
`durSec`	No	duration (default: full media length)
`volume`	No
`opacity`	No
`rotation`	No
`trackIndex`	No	target track (index in the tracks list); a new track is made if omitted
`srcStartSec`	No	in-point inside the source file, seconds
`trackRenderIndex`	No	layer order; higher = on top

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 8, 2026

TDQS

C2.6/5.0

Behavior2/5

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

No annotations are provided, so the description carries full responsibility for disclosing behavior. It only says that an audio clip is added to a track; it does not mention that this mutates the draft, whether a new track is created, whether existing audio is replaced, or what happens with the source file. 'At a time' is under-specified and does not clarify timeline behavior.

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

Conciseness3/5

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

The description is short and front-loaded, which is good for scanning, but it is too terse for a complex mutation tool with 14 parameters. The ambiguous phrase 'at a time' makes the sentence less precise, and important operational details are absent.

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

Completeness2/5

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

For a complex tool with 14 parameters, no annotations, no output schema, and many sibling tools, this description is insufficient. Required parameters are unexplained, there is no side-effect or error context, and no relationship to the draft/timeline is established. An agent would likely need to inspect schemas or guess to invoke this tool correctly.

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

Parameters2/5

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

Schema coverage is only 36%, and the description does not compensate for the gap. It does not explain the required parameters (draft, file, atSec) or the many optional placement and transform parameters. 'At a time' and 'track' loosely map to atSec and trackIndex, but this is too vague to help an agent correctly populate a 14-parameter schema.

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

Purpose4/5

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

The description uses a clear action verb ('Add') with a specific resource ('audio clip') and target ('a track'), so the core operation is understandable and distinguishable from sibling tools like capcut_add_video or capcut_add_image. However, 'at a time' is ambiguous—it could mean 'one at a time' or 'at a specific timestamp'—and no draft/timeline context is mentioned, preventing a perfect score.

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

Usage Guidelines2/5

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 instead of alternatives, no prerequisites, and no mention of audio-specific edge cases such as supported formats or where the audio file comes from. Usage is only implied by the tool name and the word 'Add,' rather than stated as a decision rule.

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

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