This record as markdown: /tools/jjpxdev-unreal-mcp/add-blueprint-function.md
What add_blueprint_function does on Unreal
AI agents use add_blueprint_function 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 |
|---|---|---|---|
function_name | string | Yes | Function name |
blueprint_path | string | Yes | Blueprint asset path |
Parameters from the server's own tool schema.
Why add_blueprint_function is rated Medium
This tool creates or modifies Blueprint functions, which are reversible changes to game logic and code structure. The action is Write-category because it adds new code elements without executing them or causing irreversible destruction.
From the tool's definition Tool name 'add_blueprint_function' and description 'Add a custom function to a Blueprint' indicate creation and modification of Blueprint code artifacts.
Attacks that exploit this kind of access
The rule that runs add_blueprint_function 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 add_blueprint_function, this is the rule to start with:
add_blueprint_function 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 add_blueprint_function call is checked against it from then on.
Questions about add_blueprint_function
Add a custom function to a Blueprint. 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.
add_blueprint_function accepts 2 parameters: function_name, blueprint_path. Required: function_name, blueprint_path. 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 add_blueprint_function: 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.
add_blueprint_function 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 add_blueprint_function 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 add_blueprint_function. 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.
add_blueprint_function 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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