Search for files and directories using regex pattern on filenames
AI agents call search_by_filename_regex to retrieve information from LocalFS MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a read-only search operation that retrieves and queries filesystem metadata. While the sibling tools include destructive operations (delete_file, delete_directory), this specific tool only searches and returns results. The regex pattern matching on filenames poses minimal risk as it cannot modify, execute, or delete data—only discover it.
From the tool's definition Tool performs pattern matching to locate files and directories with no modification capability. The description explicitly states it "search[es] for files and directories using regex pattern on filenames" with no mention of creating, modifying, or deleting…
Attacks that exploit this kind of access
Search for files and directories using regex pattern on filenames. It is categorised as a Read tool in the LocalFS MCP Server MCP Server, which means it retrieves data without modifying state.
Register the LocalFS MCP Server MCP server in PolicyLayer and add a rule for search_by_filename_regex: 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 LocalFS MCP Server. Nothing to install.
search_by_filename_regex is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the search_by_filename_regex 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 search_by_filename_regex. 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.
search_by_filename_regex is provided by the LocalFS MCP Server MCP server (mcp-bridge/local-filesystem). 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.
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