Add a standard mastering chain to the master track.
AI agents use add_mastering_chain to create or update resources in Reaper — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Reaper environment.
This tool modifies the project by adding effects to the master track. While the effects themselves can be removed (making it reversible), it is a direct modification of the audio production project state and setup. It does not execute arbitrary code or delete data, so it does not qualify as Execute or Destructive.
From the tool's definition 'Add a standard mastering chain to the master track' — this creates and inserts audio processing elements (compressors, EQs, limiters, etc.) onto the master track, modifying the project structure and signal chain irreversibly through the DAW's state.
Documented attack patterns abuse exactly the kind of access add_mastering_chain gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Reaper, and nothing reaches the server without passing your rules. This is the rule we recommend for add_mastering_chain:
{
"version": "1",
"default": "deny",
"tools": {
"add_mastering_chain": {
"limits": [
{
"counter": "add_mastering_chain_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_mastering_chain 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.
Free to start. No card required.
Add a standard mastering chain to the master track. It is categorised as a Write tool in the Reaper 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 add_mastering_chain: 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 Reaper. Nothing to install.
add_mastering_chain 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_mastering_chain 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_mastering_chain. 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_mastering_chain is provided by the Reaper MCP server (twelvetake-studios/reaper-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Reaper, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
158 Reaper tools catalogued and risk-classified — across an index of 43,000+ MCP servers.