Add marker. Prefer add_markers_batch for multiple.
AI agents use marker_add 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.
Markers are project metadata that organize timeline positions. Adding markers modifies the project structure but is reversible (markers can be deleted). This is a clear Write operation: creates data with side effects but no destruction or code execution. Severity is medium because uncontrolled marker creation could clutter a project, but impact is non-destructive and easily undone.
From the tool's definition Tool name 'marker_add' and description 'Add marker' indicate creation of new data (markers in REAPER project). The suggestion to 'Prefer add_markers_batch for multiple' confirms this is a write operation that creates markers.
Documented attack patterns abuse exactly the kind of access marker_add 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 marker_add:
{
"version": "1",
"default": "deny",
"tools": {
"marker_add": {
"limits": [
{
"counter": "marker_add_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}marker_add 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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Add marker. Prefer add_markers_batch for multiple. 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 marker_add: 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.
marker_add 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 marker_add 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 marker_add. 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.
marker_add 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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