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Audio-to-Video

audio_to_video_create_video

MCP guidance:

  • Starts an async video job; returns id and credits_charged. For finished results, call wait_for_video_project with that id or poll GET /v1/video-projects/{id} until complete, error, or canceled. Results include downloads; wait helpers add exact_download_urls. Preserve signed URLs and query parameters; never append expiration metadata.

  • For *_file_path, use an existing Magic Hour path or the upload-URL endpoint's file_path after uploading raw bytes to its presigned URL. Direct public media URLs may work if stable and fetchable as raw bytes; hotlinked URLs can fail. Prefer the upload-URL endpoint when unsure.

What this API does

Create the same Audio To Video you can make in the browser, but programmatically, so you can automate it, run it at scale, or connect it to your own app or workflow.

Good for

  • Automation and batch processing

  • Adding audio to video into apps, pipelines, or tools

How it works (3 steps)

  1. Upload your inputs (video, image, or audio) with Generate Upload URLs and copy the file_path.

  2. Send a request to create a audio to video job with the basic fields.

  3. Check the job status until it's complete, then download the result from downloads.

Key options

  • Inputs: usually a file, sometimes a YouTube link, depending on project type

  • Resolution: output size and plan requirements vary by workflow and model. Some workflows derive output size from the input video.

  • Extra fields: e.g. face_swap_mode, start_seconds/end_seconds, or a text prompt

Cost
Credits are charged when the job is queued (credits_charged in the response). Tools billed per frame charge an estimate and settle to the frames that actually render once the job finishes; tools billed per second charge the final amount upfront. Failed jobs are refunded.

For detailed examples, see the product page.

Input Schema

NameRequiredDescriptionDefault
nameNoGive your video a custom name for easy identification.Audio To Video - dateTime
styleNoAttributes used to dictate the style of the output
assetsYesProvide the audio file and an optional reference image.
resolutionNoOutput video resolution. Defaults to `720p` on paid tiers and `480p` on free tiers.
end_secondsYesEnd time of your clip (seconds). Must be greater than start_seconds.
start_secondsNoStart time of your clip (seconds). Must be ≥ 0.

Output Schema

NameRequiredDescriptionDefault
idYesUnique ID of the video. Use it with the [Get video Project API](https://docs.magichour.ai/api-reference/video-projects/get-video-details) to fetch status and downloads.
credits_chargedYesThe amount of credits deducted from your account to generate the video. If the status is not 'complete', this value is an estimate and may be adjusted upon completion based on the actual FPS of the output video. If video generation fails, credits will be refunded, and this field will be updated to include the refund.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changed
    • changedInput schema / properties / assets / properties / audio_file_path / description
      Previous value: -"The path of the audio file. This value is either\n- a direct URL to the video file\n- `file_path` field from the response of the [upload urls API](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls).\n\nSee the [file upload guide](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls#input-file) for details.\n"New value: +"The path of the audio file. This value is either\n- a direct URL to the file. The URL path must end in a supported file extension.\n- `file_path` field from the response of the [upload urls API](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls).\n\nSee the [file upload guide](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls#input-file) for details.\n"
    • changedInput schema / properties / assets / properties / image_file_path / description
      Previous value: -"Reference image for the initial frame of the video. This value is either\n- a direct URL to the video file\n- `file_path` field from the response of the [upload urls API](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls).\n\nSee the [file upload guide](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls#input-file) for details.\n"New value: +"Reference image for the initial frame of the video. This value is either\n- a direct URL to the file. The URL path must end in a supported file extension.\n- `file_path` field from the response of the [upload urls API](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls).\n\nSee the [file upload guide](https://docs.magichour.ai/api-reference/files/generate-asset-upload-urls#input-file) for details.\n"
  2. Changed2 schema fields changed
    • changedInput schema / properties / end_seconds / example
      Previous value: -15New value: +5
    • changedInput schema / properties / resolution / example
      Previous value: -"720p"New value: +"480p"
  3. Changed1 schema field changed
    • removedInput schema / properties / context
      Removed value: -{
-  "description": "Explain in 15-25 words, in third person, why this tool is called and how it supports the user's goal. For analytics only. You MUST describe only the abstract purpose of the tool call. NEVER include, repeat, paraphrase, or infer personal, sensitive, or identifying information from the user request or tool results, including names, emails, phone numbers, IPs, IDs, or credentials. You MUST generalize specific entities into roles such as \"a user\", \"the customer\", or \"an account\". Example: \"Retrieving a customer's recent orders to investigate a billing issue and help support determine the appropriate resolution.\"",
-  "type": "string"
-}
  4. Changed1 schema field changed
    • addedInput schema / properties / context
      Added value: +{
+  "description": "Explain in 15-25 words, in third person, why this tool is called and how it supports the user's goal. For analytics only. You MUST describe only the abstract purpose of the tool call. NEVER include, repeat, paraphrase, or infer personal, sensitive, or identifying information from the user request or tool results, including names, emails, phone numbers, IPs, IDs, or credentials. You MUST generalize specific entities into roles such as \"a user\", \"the customer\", or \"an account\". Example: \"Retrieving a customer's recent orders to investigate a billing issue and help support determine the appropriate resolution.\"",
+  "type": "string"
+}
  5. First observed

TDQS

A4.6/5.0
Behavior5/5

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

Beyond annotations, the description discloses that the job is asynchronous, returns id and credits_charged, has complete/error/canceled states, provides downloads, and that wait helpers add exact_download_urls. It also explains credit charging, per-frame estimates, refunds for failed jobs, and signed-URL handling constraints.

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

Conciseness4/5

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

The description is long but front-loads the operational guidance about async jobs, waiting, and file paths before the explanatory sections. Some marketing-style material such as browser parity and automation benefits could be trimmed, but the structure is logical and most content earns its place for a complex async job tool.

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

Completeness5/5

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

Given the async workflow, credit charging, upload prerequisites, and output schema already present, the description covers what an agent still needs: job lifecycle, status handling, download behavior, and file path constraints. No critical invocation detail appears missing.

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 description coverage is 100%, so the schema already documents each parameter thoroughly. The description still adds useful behavioral semantics for *_file_path values, including preferred upload-URL flow and the risk of hotlinked public URLs, which goes beyond the schema text.

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?

The description names a specific verb and resource — create an Audio To Video project programmatically — and the input schema confirms audio_file_path as the required core asset. An agent can distinguish this from sibling video-creation tools because the purpose is explicitly audio-driven video generation.

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

Usage Guidelines4/5

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

It gives clear usage context: upload first, create the job, then call wait_for_video_project or poll the project endpoint. It also routes file-path handling toward the upload-URL endpoint when uncertain. It does not explicitly contrast when to use this versus text_to_video or image_to_video, so it falls short of full alternative guidance.

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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