Replace a string in a file. Fails if old_string is not found. Set replace_all=true to replace every occurrence.
AI agents use fs_edit to create or update resources in Taw Computer — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Taw Computer environment.
This tool creates or modifies data reversibly by replacing content within files. While the modification itself cannot be undone without external version control, the operation is not inherently destructive (the original file is not deleted, and the change could theoretically be reverted by replacing the new string back with the old one).
From the tool's definition Tool description states it 'Replace[s] a string in a file', which is a reversible modification operation. The tool modifies file contents via string replacement.
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access fs_edit gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Taw Computer, and nothing reaches the server without passing your rules. This is the rule we recommend for fs_edit:
{
"version": "1",
"default": "deny",
"tools": {
"fs_edit": {
"limits": [
{
"counter": "fs_edit_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fs_edit 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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Replace a string in a file. Fails if old_string is not found. Set replace_all=true to replace every occurrence. It is categorised as a Write tool in the Taw Computer MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Taw Computer MCP server in PolicyLayer and add a rule for fs_edit: 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 Taw Computer. Nothing to install.
fs_edit 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 fs_edit 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 fs_edit. 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.
fs_edit is provided by the Taw Computer MCP server (tawgroup/taw-computer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Taw Computer, 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.
36 Taw Computer tools catalogued and risk-classified — across an index of 43,000+ MCP servers.