CapCut MCP Server

by bchenner

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Python

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capcut_add_audio_clip

Add voiceover, background music, or SFX to a CapCut draft by choosing the audio path, start time, volume, and track.

Instructions

Add an audio clip (clean voiceover, background music, SFX) to the CapCut draft.

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_name": "<draft_name>",
      "audio_path": "<audio_path>"
    },
    "name": "capcut_add_audio_clip"
  }
}

Input Schema

Name	Required	Description	Default
`volume`	No
`start_ms`	No
`audio_path`	Yes
`draft_name`	Yes
`duration_ms`	No
`track_index`	No
`source_start_ms`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 11, 2026

TDQS

C2.7/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full burden for a mutation tool. It does not disclose whether the clip is appended or inserted, how track_index collisions are handled, whether existing audio is affected, or any permission/overwrite behavior.

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?

A single front-loaded sentence with the action first and parenthetical examples that earn their place. No filler.

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 7-parameter mutation tool with no annotations and 0% schema coverage, the description is far too thin; the only relief is that an output schema exists so return values need not be explained. The parameter surface is effectively undocumented.

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

Parameters1/5

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

Schema description coverage is 0% across 7 parameters (volume, start_ms, duration_ms, track_index, source_start_ms, audio_path, draft_name), and the description adds no meaning for any of them. An agent gets no guidance on units, defaults, or the distinction between start_ms and source_start_ms.

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 gives a specific verb ('Add'), resource ('audio clip'), and destination ('to the CapCut draft'), plus concrete examples (voiceover, background music, SFX). It does not, however, distinguish itself from the overlapping sibling capcut_add_bg_music_with_ducking, which also handles background music.

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?

The example audio categories hint at use cases, but the description never states when to choose this generic add over siblings like capcut_add_bg_music_with_ducking or capcut_improve_audio. No prerequisites or exclusions are given.

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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