create_prefab
Save an existing GameObject as a real .prefab file — FULL engine serialization: every component with its property values, and all children, in the same JSON format the editor writes. Returns { created, path, sourceId, components, children } — pass path to instantiate_prefab to spawn copies or get...
This record as markdown: /tools/sbox/create-prefab.md
What create_prefab does on Sbox
AI agents use create_prefab to create or update resources in Sbox, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Sbox environment.
Why create_prefab is rated Medium
Creates or modifies game asset files reversibly; overwrites risk warrants high severity.
From the tool's definition Save GameObject as .prefab file, overwrites existing file at path.
Risk signalsBulk/mass operation — affects multiple targets
Attacks that exploit this kind of access
The rule that runs create_prefab safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Sbox, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For create_prefab, this is the rule to start with:
create_prefab 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 Sbox, apply this rule, and every create_prefab call is checked against it from then on.
Questions about create_prefab
Save an existing GameObject as a real .prefab file — FULL engine serialization: every component with its property values, and all children, in the same JSON format the editor writes. Returns { created, path, sourceId, components, children } — pass path to instantiate_prefab to spawn copies or get_prefab_info to inspect. Errors if the source GameObject is missing; overwrites an existing file at path. It is categorised as a Write tool in the Sbox MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Sbox MCP server in PolicyLayer and add a rule for create_prefab: 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 Sbox. Nothing to install.
create_prefab 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 create_prefab 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 create_prefab. 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.
create_prefab is provided by the Sbox MCP server (sbox-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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