Replace a unique string in a file with another string. The string to replace must appear exactly once in the file.
AI agents use str_replace to create or update resources in OODA Computer Control — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your OODA Computer Control environment.
This tool creates or modifies data (file contents) in a reversible manner, fitting the Write category. Severity is high because modifying file contents could corrupt configuration files, source code, or other critical data if an AI agent targets the wrong file or makes incorrect replacements.
From the tool's definition Tool description states it will 'Replace a unique string in a file with another string,' which modifies file contents. The tool performs reversible file modifications without deletion.
Documented attack patterns abuse exactly the kind of access str_replace gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and OODA Computer Control, and nothing reaches the server without passing your rules. This is the rule we recommend for str_replace:
{
"version": "1",
"default": "deny",
"tools": {
"str_replace": {
"limits": [
{
"counter": "str_replace_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}str_replace 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 unique string in a file with another string. The string to replace must appear exactly once in the file. It is categorised as a Write tool in the OODA Computer Control MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the OODA Computer Control MCP server in PolicyLayer and add a rule for str_replace: 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 OODA Computer Control. Nothing to install.
str_replace 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 str_replace 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 str_replace. 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.
str_replace is provided by the OODA Computer Control MCP server (mnehmos/mnehmos.ooda.mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from OODA Computer Control, 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.
99 OODA Computer Control tools catalogued and risk-classified — across an index of 43,000+ MCP servers.