Copy a range of lines from one file and insert the copy into a different file after a given line number. Original lines in the source are preserved. Use to combine content from two files without manually rewriting either.
AI agents use copy_lines_between_files to create or update resources in FilesystemMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FilesystemMCP environment.
The tool inserts content into a file, which is a write operation. It does not delete data (would be Destructive), execute code (would be Execute), or involve financial operations. While it modifies a file, the operation is reversible—the inserted lines can be removed and the file restored.
From the tool's definition Tool description states it will 'Copy a range of lines from one file and insert the copy into a different file after a given line number', which modifies the destination file.
Attacks that exploit this kind of access
Copy a range of lines from one file and insert the copy into a different file after a given line number. Original lines in the source are preserved. Use to combine content from two files without manually rewriting either. It is categorised as a Write tool in the FilesystemMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Filesystem MCP server in PolicyLayer and add a rule for copy_lines_between_files: 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 FilesystemMCP. Nothing to install.
copy_lines_between_files 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 copy_lines_between_files 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 copy_lines_between_files. 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.
copy_lines_between_files is provided by the Filesystem MCP server (rijadalisic/filesystemmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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