Captions Burn In

Immutable Catalog Entry

This descriptor comes from the active versioned Portal catalog.

WRITEffmpeg.captions_burn_in

• Contract tier: agent_ready
• Risk: write
• Catalog version: 2026-07-12.3
• Descriptor hash: 02a83f3121c6d8004b39c53e0836407616e35cb4a094c0f1948192ac067a3276

Use this to burn SRT, VTT, or timed-word captions into a staged video with bounded brand and safe-zone styling. Supply exactly one caption source; it queues a new rendered asset.

Request Body

{
  "jsonrpc": "2.0",
  "id": "ffmpeg-captions-burn-in-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.captions_burn_in",
    "arguments": {
      "asset_id": "asset_id_123",
      "position": "",
      "priority": "",
      "box_color": "",
      "font_name": "",
      "font_size": "",
      "max_chars": "",
      "max_lines": "",
      "max_words": "",
      "font_color": ""
    }
  }
}

Arguments Schema

{
  "type": "object",
  "required": [
    "asset_id"
  ],
  "properties": {
    "asset_id": {
      "type": "string",
      "description": "Stable ID of one staged FFmpeg media asset."
    },
    "position": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Approved overlay or caption position name."
    },
    "priority": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Optional queue priority configured by the server, such as urgent or batch."
    },
    "box_color": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Safe FFmpeg color used for the text background box."
    },
    "font_name": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Allowlisted server font filename or name."
    },
    "font_size": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Font size in pixels within configured minimum and maximum bounds."
    },
    "max_chars": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Maximum characters per caption line within server limits."
    },
    "max_lines": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Maximum lines in one caption cue within server limits."
    },
    "max_words": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Maximum words in one caption cue within server limits."
    },
    "font_color": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Safe FFmpeg color used for text."
    },
    "padding_px": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Caption box padding in pixels within server limits."
    },
    "words_json": {
      "anyOf": [
        {
          "type": "array",
          "items": {
            "type": "object",
            "additionalProperties": true
          }
        },
        {
          "type": "null"
        }
      ],
      "description": "Timed word objects containing word, start, and end values; provide only one caption source."
    },
    "box_opacity": {
      "anyOf": [
        {
          "type": "number"
        },
        {
          "type": "null"
        }
      ],
      "description": "Caption background opacity from 0.0 through 1.0."
    },
    "brand_kit_id": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Existing local brand-kit identifier."
    },
    "captions_srt": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Inline SRT caption text; provide only one caption source."
    },
    "captions_vtt": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Inline WebVTT caption text; provide only one caption source."
    },
    "font_asset_id": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Optional staged font asset ID used by the overlay renderer."
    },
    "highlight_mode": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Approved caption word-highlight behavior."
    },
    "highlight_color": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Safe color used for highlighted caption words."
    },
    "safe_zone_top_px": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Additional top safe-zone inset in pixels."
    },
    "safe_zone_profile": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Approved platform safe-zone profile for caption placement."
    },
    "safe_zone_bottom_px": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Additional bottom safe-zone inset in pixels."
    }
  },
  "additionalProperties": false
}

Output Schema

{
  "type": "object",
  "required": [
    "job_id",
    "cache_hit"
  ],
  "properties": {
    "job_id": {
      "type": "string",
      "description": "Stable ID used with the job readback tools."
    },
    "cache_hit": {
      "type": "boolean",
      "description": "Whether a matching completed result was reused."
    },
    "output_asset_ids": {
      "type": "array",
      "items": {
        "type": "string"
      },
      "description": "Completed output asset IDs when immediately available from cache."
    }
  },
  "additionalProperties": false
}

Code Examples

cURL

curl -X POST 'https://portal.madpanda3d.com/api/mcp' \
  -H 'Authorization: Bearer mad_live_***' \
  -H 'Content-Type: application/json' \
  -d '{
  "jsonrpc": "2.0",
  "id": "ffmpeg-captions-burn-in-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.captions_burn_in",
    "arguments": {
      "asset_id": "asset_id_123",
      "position": "",
      "priority": "",
      "box_color": "",
      "font_name": "",
      "font_size": "",
      "max_chars": "",
      "max_lines": "",
      "max_words": "",
      "font_color": ""
    }
  }
}'

Node.js

const response = await fetch('https://portal.madpanda3d.com/api/mcp', {
  method: 'POST',
  headers: {
    Authorization: 'Bearer mad_live_***',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
  "jsonrpc": "2.0",
  "id": "ffmpeg-captions-burn-in-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.captions_burn_in",
    "arguments": {
      "asset_id": "asset_id_123",
      "position": "",
      "priority": "",
      "box_color": "",
      "font_name": "",
      "font_size": "",
      "max_chars": "",
      "max_lines": "",
      "max_words": "",
      "font_color": ""
    }
  }
}),
});
const data = await response.json();
console.log(data);

Python

import requests

url = 'https://portal.madpanda3d.com/api/mcp'
headers = {
    'Authorization': 'Bearer mad_live_***',
    'Content-Type': 'application/json',
}
payload = {
  "jsonrpc": "2.0",
  "id": "ffmpeg-captions-burn-in-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.captions_burn_in",
    "arguments": {
      "asset_id": "asset_id_123",
      "position": "",
      "priority": "",
      "box_color": "",
      "font_name": "",
      "font_size": "",
      "max_chars": "",
      "max_lines": "",
      "max_words": "",
      "font_color": ""
    }
  }
}
response = requests.post(url, headers=headers, json=payload, timeout=60)
print(response.json())

Example Responses

200 Success

{
  "ok": true,
  "message": "Tool ffmpeg.captions_burn_in executed successfully.",
  "note": "Response shape varies by MCP tool. Inspect live responses for exact fields."
}

502 Upstream Error

{
  "ok": false,
  "classification": "upstream_http_error",
  "message": "Upstream MCP returned a non-success status."
}