Set project tempo.
AI agents use transport_set_bpm to create or update resources in ReaperMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your ReaperMCP environment.
This tool creates or modifies data (tempo/BPM setting) in a reversible manner. It is not destructive (the change can be undone), not financial, and not read-only since it actively changes project state. It does not execute arbitrary code or scripts.
From the tool's definition Tool name 'transport_set_bpm' and description 'Set project tempo' indicate modification of project settings. The verb 'set' denotes a write operation that changes state. This is a REAPER music production tool that modifies a core project parameter.
Documented attack patterns abuse exactly the kind of access transport_set_bpm 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 transport_set_bpm:
{
"version": "1",
"default": "deny",
"tools": {
"transport_set_bpm": {
"limits": [
{
"counter": "transport_set_bpm_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}transport_set_bpm 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.
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Set project tempo. It is categorised as a Write tool in the ReaperMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Reaper MCP server in PolicyLayer and add a rule for transport_set_bpm: 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.
transport_set_bpm 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 transport_set_bpm 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 transport_set_bpm. 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.
transport_set_bpm 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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138 ReaperMCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.