Magic Hour

Add subtitles to video

add_subtitles_to_video

Adds automatically generated subtitles to a supplied video segment using a subtitle preset or custom text styling. Starts a background job that costs credits; returns a project id for wait_for_video_project.

Input Schema

Name	Required	Description	Default
`name`	No	Give your video a custom name for easy identification.	Auto Subtitle - dateTime
`style`	Yes	Style of the subtitle. At least one of `.style.template` or `.style.custom_config` must be provided. * If only `.style.template` is provided, default values for the template will be used. * If both are provided, the fields in `.style.custom_config` will be used to overwrite the fields in `.style.template`. * If only `.style.custom_config` is provided, then all fields in `.style.custom_config` will be used. To use custom config only, the following `custom_config` params are required: * `.style.custom_config.font` * `.style.custom_config.text_color` * `.style.custom_config.vertical_position` * `.style.custom_config.horizontal_position`
`assets`	Yes	Provide the assets for auto subtitle generator
`end_seconds`	Yes	End time of your clip (seconds). Must be greater than start_seconds.
`start_seconds`	Yes	Start time of your clip (seconds). Must be ≥ 0.

Output Schema

Name	Required	Description	Default
`id`	Yes	Unique 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_charged`	Yes	The 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.

AddedOct 30, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already cover safety (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds genuinely new behavior: it runs as a background job, it consumes credits, and it returns a project id. It stops short of saying anything about job duration or failure handling, so not a 5.

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?

Two sentences, zero filler, with the core action front-loaded and the cost/async consequence trailing. Nothing could be cut without losing information.

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

Completeness4/5

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

Output schema exists, so return-value explanation is not required, and the description still links the job to wait_for_video_project. The one gap is not flagging the overlap with translate_video for a tool that sits among many similar video generators.

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

Parameters3/5

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

Schema coverage is 100% and the style enum, custom_config requirements, and asset path rules are all documented in the schema itself. The description only echoes the preset-vs-custom choice, adding no new format or constraint detail, so baseline 3 applies.

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?

States a specific verb and resource ('Adds automatically generated subtitles to a supplied video segment') plus the two styling modes, which is enough to separate it from generic siblings like edit_video or restyle_video.

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

Usage Guidelines3/5

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

It names the follow-up tool (wait_for_video_project) and flags that the job costs credits, but never says when to pick this over a close alternative such as translate_video, which also produces subtitles. Usage is therefore implied rather than guided.

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

All Magic Hour tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.