AI agents invoke bounce_stems to trigger actions in ReaperMCP. 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.
'Bouncing stems' in music production means rendering/exporting individual track groups to audio files, which is an execution/render operation that triggers audio processing and file writes. Without a description, confidence is lowered, but the name strongly implies triggering an export/render process in REAPER, which falls under Execute (running an external operation).
From the tool's definition Tool name 'bounce_stems' in a music production context; description is empty and uninformative.
Documented attack patterns abuse exactly the kind of access bounce_stems gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ReaperMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for bounce_stems:
{
"version": "1",
"default": "deny",
"tools": {
"bounce_stems": {
"limits": [
{
"counter": "bounce_stems_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}bounce_stems 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.
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bounce_stems. It is categorised as a Execute tool in the ReaperMCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Reaper MCP server in PolicyLayer and add a rule for bounce_stems: 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 ReaperMCP. Nothing to install.
bounce_stems 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 bounce_stems 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 bounce_stems. 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.
bounce_stems is provided by the Reaper MCP server (xdarkzx/reaper-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ReaperMCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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