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obs_set_source_transform

Position and size a scene source precisely to build picture-in-picture or side-by-side layouts, with coordinates in canvas pixels.

Instructions

Position and size a source inside a scene, to build picture-in-picture and side-by-side layouts. Coordinates are in canvas pixels.

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": {
      "sceneName": "<sceneName>",
      "sceneItemId": "<sceneItemId>"
    },
    "name": "obs_set_source_transform"
  }
}

Input Schema

Name	Required	Description	Default
`scaleX`	No
`scaleY`	No
`cropTop`	No
`cropLeft`	No
`cropRight`	No
`positionX`	No
`positionY`	No
`sceneName`	Yes
`cropBottom`	No
`sceneItemId`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 20, 2026

TDQS

B3.2/5.0

Behavior3/5

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

With no annotations provided, the description is responsible for deciding behavioral expectations. It adds a genuinely useful fact—'Coordinates are in canvas pixels'—which helps the agent understand the coordinate frame. But it does not disclose whether unspecified transform parameters are preserved or reset, nor does it explain any prerequisites or side effects beyond the obvious 'set' operation.

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?

The description is two sentences, front-loaded with the primary action and an explicit use case. It avoids filler and every sentence contributes meaningful information.

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?

This is a 10-parameter, mutation-oriented tool with no annotations and no output schema, which places a heavy responsibility on the description. The short text offers only high-level guidance and does not explain the interaction of parameters, the coordinate origin, units as they apply to crops/scale, or the behavior for omitted values. It is not adequate for an agent to confidently select and invoke the tool across the full parameter space.

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?

There are 10 parameters and the input schema provides 0% description coverage, so the tool description must compensate. It broadly signals that position and size are controlled, and the canvas-pixel coordinate note assists with position parameters, but scale fields, crop values, and their units/meaning are left entirely to names. This is not enough to support correct usage of the full parameter set.

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 clearly states the operation with specific verbs ('position and size') and a concrete resource ('a source inside a scene'), and it adds a practical use case ('picture-in-picture and side-by-side layouts'). It is not quite a 5 because the sibling tool `obs_scene_item_transform` likely overlaps in functionality, and the description does not explicitly distinguish when to use one over the other.

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?

The description gives a clear intended context by mentioning picture-in-picture and side-by-side layouts, which tells the agent when to consider this tool. However, it gives no exclusions or alternatives, and the existence of a sibling named `obs_scene_item_transform` makes the absence of explicit comparison guidance more impactful.

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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