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ue5_call_function

Call any UFUNCTION on a UObject in Unreal Engine 5 via the Web Remote Control API. Use actor-level functions like SetActorScale3D for reliable remote execution.

Instructions

Calls a UFUNCTION on a UObject via the Web Remote Control API. IMPORTANT: Some functions on component sub-objects (e.g., LightComponent, RootComponent) are marked 'unavailable remotely'. Use actor-level functions like SetActorScale3D, SetActorTransform instead.

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": {
      "objectPath": "<objectPath>",
      "functionName": "<functionName>"
    },
    "name": "ue5_call_function"
  }
}

Input Schema

Name	Required	Description
`objectPath`	Yes	The path to the UObject (e.g., '/Game/Maps/MyMap.MyMap:PersistentLevel.MyActor_1', or '/Script/UnrealEd.Default__EditorActorSubsystem' for editor subsystems).
`functionName`	Yes	The name of the function to call.
`parameters`	No	JSON object containing the function parameters.
`generateTransaction`	No	If true, the operation can be undone with Ctrl+Z in the editor. Default: true for write operations.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Jun 18, 2026

TDQS

B3.4/5.0

Behavior2/5

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

No annotations are provided, so the description carries full burden for behavioral disclosure. It only mentions the API and a remote unavailability constraint. It fails to address crucial aspects like side effects, destructiveness, permissions, or return behavior for a tool that can execute arbitrary code.

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 consists of two well-structured sentences: the first states the core purpose, and the second provides a critical usage warning. There is no redundancy or extraneous 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?

Given the tool's complexity (4 parameters, nested objects, no output schema), the description is insufficient. It does not explain the return value, the transactional aspect (generateTransaction), or how to properly format objectPath beyond what is in the schema. Critical context for safe and effective use is missing.

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%, so the input schema already describes all parameters. The description adds no extra meaning beyond the general context of calling a function via remote API, thus the baseline of 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?

The description clearly states the tool calls a UFUNCTION on a UObject via the Web Remote Control API, using a specific verb and resource. It distinguishes itself from sibling tools which are specialized actions, making its generic function-call purpose unmistakable.

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 includes an important warning about component sub-objects being unavailable remotely and recommends actor-level functions instead. However, it does not provide explicit when-to-use or when-not-to-use guidance relative to other siblings, leaving some ambiguity.

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