set_blueprint_property
Set a default property value on a Blueprint's CDO (Class Default Object). For component properties, use a dot path like 'ComponentName.PropertyName'.
This record as markdown: /tools/jjpxdev-unreal-mcp/set-blueprint-property.md
What set_blueprint_property does on Unreal
AI agents use set_blueprint_property to create or update resources in Unreal, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Unreal environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
property_name | string | Yes | Property name, or ComponentName.PropertyName for component sub-properties |
blueprint_path | string | Yes | Blueprint asset path |
property_value | string | Yes | Property value — asset paths (/Game/...), Python expressions (True, 42.0), or plain strings |
Parameters from the server's own tool schema.
Why set_blueprint_property is rated Medium
An AI agent can call set_blueprint_property faster than any human can review: one bad instruction and it creates or modifies resources in Unreal by the hundred, each call as confident as the last.
Attacks that exploit this kind of access
The rule that runs set_blueprint_property safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Unreal, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For set_blueprint_property, this is the rule to start with:
set_blueprint_property stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Unreal, apply this rule, and every set_blueprint_property call is checked against it from then on.
Questions about set_blueprint_property
Set a default property value on a Blueprint's CDO (Class Default Object). For component properties, use a dot path like 'ComponentName.PropertyName'. It is categorised as a Write tool in the Unreal MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
set_blueprint_property accepts 3 parameters: property_name, blueprint_path, property_value. Required: property_name, blueprint_path, property_value. The full parameter table on this page comes from the server's own tool schema.
Register the Unreal MCP server in PolicyLayer and add a rule for set_blueprint_property: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Unreal. Nothing to install.
set_blueprint_property is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the set_blueprint_property rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for set_blueprint_property. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
set_blueprint_property is provided by the Unreal MCP server (@jjpxdev/unreal-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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