editor.metasound

Ten methods covering UE's MetaSound procedural audio pipeline -- asset discovery, source and patch builder lifecycle, I/O pin introspection, and interface registry queries. AI agents reach through this namespace to create and wire MetaSound graphs without opening the MetaSound editor.

← API Reference

Requires: the MetaSound plugin (enabled by default on stock UE). If not enabled, all methods return -32001 NotFound with guidance to enable MetaSound in Edit > Plugins.

Method summary

Method	Mutating	Tier	Purpose
`listAssets`	no	Free	Find all MetaSound source assets in the project.
`getInfo`	no	Free	Per-asset introspection: input/output counts, interfaces, preset flag.
`createSource`	yes	Free	Create and register a MetaSound source builder.
`createPatch`	yes	Free	Create and register a MetaSound patch builder.
`findBuilder`	no	Free	Look up a registered builder by name.
`unregisterBuilder`	yes	Free	Unregister a named builder.
`getRegisteredBuilders`	no	Free	List all registered builders via the asset registry.
`getInputs`	no	Free	Graph input pins of a registered builder.
`getOutputs`	no	Free	Graph output pins of a registered builder.
`isInterfaceRegistered`	no	Free	Check whether a MetaSound interface is registered in the system.

`editor.metasound.listAssets`

Find all MetaSound source assets in the project, optionally filtered to a package path.

Parameters:

Name	Type	Required	Description
`path_filter`	string	No	Package path filter (e.g. `/Game/Audio`).

Returns:

Field	Type	Description
`assets`	array	Each: `{name, path, class, packagePath}`.
`count`	number	Number of MetaSound assets found.

Example Request:

{ "jsonrpc": "2.0", "id": 1, "method": "editor.metasound.listAssets", "params": {} }

Example Response:

{
  "jsonrpc": "2.0", "id": 1,
  "result": {
    "assets": [
      { "name": "MSS_PlayRandom_Loop", "path": "/Metasound/DefaultAssets/Sources/MSS_PlayRandom_Loop.MSS_PlayRandom_Loop", "class": "MetaSoundSource", "packagePath": "/Metasound/DefaultAssets/Sources/MSS_PlayRandom_Loop" }
    ],
    "count": 1
  }
}

`editor.metasound.getInfo`

Return per-asset metadata and introspection: whether the asset implements the MetaSound document interface, builder attachability, preset flag, input/output counts, and declared interfaces.

Parameters:

Name	Type	Required	Description
`asset_path`	string	Yes	Full asset path to a MetaSound source.

Returns:

Field	Type	Description
`asset_name`	string	Asset name.
`class`	string	UE class name.
`path`	string	Asset path.
`is_metasound`	bool	Whether the asset implements the MetaSound document interface.
`has_builder`	bool	Whether a builder could be attached.
`is_preset`	bool	Whether the asset is a preset (if a builder is attached).
`input_count`	number	Number of graph inputs.
`output_count`	number	Number of graph outputs.
`interfaces`	array	Declared MetaSound interface names.

Example Request:

{
  "jsonrpc": "2.0", "id": 2,
  "method": "editor.metasound.getInfo",
  "params": { "asset_path": "/Metasound/DefaultAssets/Sources/MSS_PlayRandom_Loop.MSS_PlayRandom_Loop" }
}

Example Response:

{
  "jsonrpc": "2.0", "id": 2,
  "result": {
    "asset_name":   "MSS_PlayRandom_Loop",
    "class":        "MetaSoundSource",
    "path":         "/Metasound/DefaultAssets/Sources/MSS_PlayRandom_Loop.MSS_PlayRandom_Loop",
    "is_metasound": true,
    "has_builder":  true,
    "is_preset":    false,
    "input_count":  3,
    "output_count": 2,
    "interfaces":   ["MetaSound", "MetaSoundSource"]
  }
}

`editor.metasound.createSource`

Create and register a new MetaSound source builder. The returned builder_name is the handle used by every other builder method in this namespace.

Parameters:

Name	Type	Required	Description
`name`	string	Yes	Builder name.
`format`	string	No	Audio format: `mono` (default) or `stereo`.
`one_shot`	bool	No	Whether the source is one-shot. Default `false`.

Returns:

Field	Type	Description
`builder_name`	string	Registered builder name.
`success`	bool	Whether creation succeeded.
`format`	string	Audio output format.
`one_shot`	bool	One-shot flag.
`audio_output_count`	number	Number of audio output pins.

Example Request:

{
  "jsonrpc": "2.0", "id": 3,
  "method": "editor.metasound.createSource",
  "params": { "name": "MySource", "format": "stereo" }
}

Example Response:

{
  "jsonrpc": "2.0", "id": 3,
  "result": { "builder_name": "MySource", "success": true, "format": "stereo", "one_shot": false, "audio_output_count": 2 }
}

`editor.metasound.createPatch`

Create and register a new MetaSound patch builder.

Parameters:

Name	Type	Required	Description
`name`	string	Yes	Builder name.

Returns: { builder_name, success }.

Example Request:

{ "jsonrpc": "2.0", "id": 4, "method": "editor.metasound.createPatch", "params": { "name": "MyPatch" } }

Example Response:

{ "jsonrpc": "2.0", "id": 4, "result": { "builder_name": "MyPatch", "success": true } }

`editor.metasound.findBuilder`

Look up a registered builder by name. Safely probes for existence before calling other builder methods.

Parameters:

Name	Type	Required	Description
`name`	string	Yes	Builder name to find.

Returns:

Field	Type	Description
`found`	bool	Whether the builder was found.
`name`	string	Builder name echo.
`builder_class`	string	UE class name if found.
`is_source`	bool	Whether it is a source builder.
`is_patch`	bool	Whether it is a patch builder.
`is_preset`	bool	Whether it is a preset builder.

Example Request:

{ "jsonrpc": "2.0", "id": 5, "method": "editor.metasound.findBuilder", "params": { "name": "MySource" } }

Example Response:

{
  "jsonrpc": "2.0", "id": 5,
  "result": { "found": true, "name": "MySource", "builder_class": "MetaSoundSourceBuilder", "is_source": true, "is_patch": false, "is_preset": false }
}

`editor.metasound.unregisterBuilder`

Unregister a named builder from the subsystem.

Parameters:

Name	Type	Required	Description
`name`	string	Yes	Builder name to unregister.

Returns: { success, name }.

Example Request:

{ "jsonrpc": "2.0", "id": 6, "method": "editor.metasound.unregisterBuilder", "params": { "name": "MySource" } }

Example Response:

{ "jsonrpc": "2.0", "id": 6, "result": { "success": true, "name": "MySource" } }

`editor.metasound.getRegisteredBuilders`

List every registered named builder discoverable through the asset registry.

No parameters.

Returns:

Field	Type	Description
`builders`	array	Each: `{name, class, is_source, is_patch}`.
`count`	number	Number of builders found.

Example Request:

{ "jsonrpc": "2.0", "id": 7, "method": "editor.metasound.getRegisteredBuilders", "params": {} }

Example Response:

{
  "jsonrpc": "2.0", "id": 7,
  "result": {
    "builders": [
      { "name": "MySource", "class": "MetaSoundSourceBuilder", "is_source": true,  "is_patch": false },
      { "name": "MyPatch",  "class": "MetaSoundPatchBuilder",  "is_source": false, "is_patch": true  }
    ],
    "count": 2
  }
}

`editor.metasound.getInputs`

Return graph input pins of a registered builder.

Parameters:

Name	Type	Required	Description
`name`	string	Yes	Builder name.

Returns:

Field	Type	Description
`inputs`	array	Each: `{name, data_type}`.
`count`	number	Number of inputs.
`builder_name`	string	Echo of the input name.

Example Request:

{ "jsonrpc": "2.0", "id": 8, "method": "editor.metasound.getInputs", "params": { "name": "MySource" } }

Example Response:

{
  "jsonrpc": "2.0", "id": 8,
  "result": {
    "inputs": [
      { "name": "Frequency", "data_type": "Float" },
      { "name": "Trigger",   "data_type": "Trigger" }
    ],
    "count": 2,
    "builder_name": "MySource"
  }
}

`editor.metasound.getOutputs`

Return graph output pins of a registered builder.

Parameters:

Name	Type	Required	Description
`name`	string	Yes	Builder name.

Returns: { outputs: [{name, data_type}], count, builder_name }.

Example Request:

{ "jsonrpc": "2.0", "id": 9, "method": "editor.metasound.getOutputs", "params": { "name": "MySource" } }

Example Response:

{
  "jsonrpc": "2.0", "id": 9,
  "result": {
    "outputs": [
      { "name": "OutAudioLeft",  "data_type": "Audio" },
      { "name": "OutAudioRight", "data_type": "Audio" }
    ],
    "count": 2,
    "builder_name": "MySource"
  }
}

`editor.metasound.isInterfaceRegistered`

Check whether a MetaSound interface is registered in the system.

Parameters:

Name	Type	Required	Description
`interface_name`	string	Yes	Interface name (e.g. `MetaSound`).

Returns: { registered, interface_name }.

Example Request:

{ "jsonrpc": "2.0", "id": 10, "method": "editor.metasound.isInterfaceRegistered", "params": { "interface_name": "MetaSound" } }

Example Response:

{ "jsonrpc": "2.0", "id": 10, "result": { "registered": true, "interface_name": "MetaSound" } }

API Reference index
editor.sound -- sound cues, classes, submixes, attenuation, playback
editor.render -- Movie Render Queue for offline audio-bearing renders

editor.metasound

Method summary

editor.metasound.listAssets

editor.metasound.getInfo

editor.metasound.createSource

editor.metasound.createPatch

editor.metasound.findBuilder

editor.metasound.unregisterBuilder

editor.metasound.getRegisteredBuilders

editor.metasound.getInputs

editor.metasound.getOutputs

editor.metasound.isInterfaceRegistered

Related

`editor.metasound.listAssets`

`editor.metasound.getInfo`

`editor.metasound.createSource`

`editor.metasound.createPatch`

`editor.metasound.findBuilder`

`editor.metasound.unregisterBuilder`

`editor.metasound.getRegisteredBuilders`

`editor.metasound.getInputs`

`editor.metasound.getOutputs`

`editor.metasound.isInterfaceRegistered`