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Giancarlo26

obs-action-history

by Giancarlo26

obs_scene_item_add

Add an existing source into a scene as a new scene item, reusing one camera or overlay across multiple scenes. New item lands on top of the z-order, so check the returned index.

Instructions

Add an EXISTING source to a scene, as a new scene item. This is the missing half of obs_create_input: that one makes a brand new source, this one places a source you already have into another scene. Reusing a source is almost always what you want - one camera placed in six scenes is one device opened once, while six separate inputs on the same webcam will fight over the device and most will fail to start.

A scene can be added to another scene this way, which is how layer scenes work: on the reference machine the HUD scene holds every overlay and is added as a SINGLE item into each scene, so editing HUD once changes all of them. Do not rebuild overlays per scene.

The new item lands at the TOP of the z-order and covers whatever it overlaps. If you are adding a background it has to be moved down to index 0 afterwards with obs_scene_item_order. The response reports the index it actually received, so check it rather than assuming.

sceneItemEnabled defaults to true. Note that a source can be enabled but sitting off-canvas: see obs_scene_item_transform for why that is not the same as hidden.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
enabledNoStart visible. Default true.
sceneNameYesScene to add the source to.
sourceNameYesName of an existing input or scene (obs_list_inputs / obs_list_scenes).
Behavior5/5

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

With no annotations provided, the description carries the full burden and excels. It discloses z-order placement ('lands at the TOP'), default enabled behavior, and clarifies the difference between being enabled and being off-canvas, plus the need for obs_scene_item_order for repositioning.

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 well-structured and front-loaded with the primary purpose, then elaborates with examples and behavioral notes. Every sentence adds value; there is no fluff or redundancy, and it is appropriately sized for the tool's complexity.

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?

For a tool with 3 params, no annotations, and no output schema, the description is remarkably complete. It covers purpose, usage alternatives, z-order behavior, default states, and interactions with other tools (obs_scene_item_order). The only minor gap is lack of error scenarios, but given the rich context, it feels sufficient.

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 coverage is 100%, so baseline is 3. The description adds meaningful context beyond schema by explaining the semantic of 'existing source' and the implications of reuse, as well as the enabled default and response index behavior. This goes beyond simple parameter descriptions.

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 clearly states the specific action: 'Add an EXISTING source to a scene, as a new scene item.' It differentiates from obs_create_input by explaining the distinction ('missing half') and provides context on reuse, making it distinct from sibling tools.

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

Usage Guidelines5/5

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

Explicit guidance on when to use this tool vs creating new inputs: 'Reusing a source is almost always what you want...' It also gives concrete examples of scene nesting and warns against rebuilding overlays, providing clear when-to-use and when-not-to-use 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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