AI agents use add_notes_by_index to create or update resources in MIDI File MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MIDI File MCP environment.
This tool creates or modifies MIDI note data within a file. While it changes file content, the operation is reversible (notes can be edited, removed, or the file re-saved). It does not execute arbitrary code, delete data irreversibly, or involve financial transactions.
From the tool's definition Tool name includes 'add_' prefix and description states 'Add notes to midi file', indicating creation/modification of data within a MIDI file structure.
Documented attack patterns abuse exactly the kind of access add_notes_by_index gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MIDI File MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for add_notes_by_index:
{
"version": "1",
"default": "deny",
"tools": {
"add_notes_by_index": {
"limits": [
{
"counter": "add_notes_by_index_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_notes_by_index 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 notes to midi file by track index. It is categorised as a Write tool in the MIDI File MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MIDI File MCP server in PolicyLayer and add a rule for add_notes_by_index: 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 MIDI File MCP. Nothing to install.
add_notes_by_index 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_notes_by_index 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_notes_by_index. 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_notes_by_index is provided by the MIDI File MCP server (xiaolaa2/midi-file-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MIDI File MCP, 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.
11 MIDI File MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.