instantiate_prefab
Spawn a FULL prefab instance into the active scene — components and children recreated. Uses the engine
This record as markdown: /tools/sbox/instantiate-prefab.md
What instantiate_prefab does on Sbox
AI agents invoke instantiate_prefab to trigger actions in Sbox. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
Why instantiate_prefab is rated High
Spawns objects with components and children into active scene, triggering engine-side execution.
From the tool's definition Spawn a FULL prefab instance into the active scene
Attacks that exploit this kind of access
The rule that runs instantiate_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 instantiate_prefab, this is the rule to start with:
instantiate_prefab stays usable, but rate-capped: a runaway agent can't fire it dozens of times 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 instantiate_prefab call is checked against it from then on.
Questions about instantiate_prefab
Spawn a FULL prefab instance into the active scene — components and children recreated. Uses the engine. It is categorised as a Execute tool in the Sbox MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Sbox MCP server in PolicyLayer and add a rule for instantiate_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.
instantiate_prefab is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the instantiate_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 instantiate_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.
instantiate_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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