AI agents use WriteIfEmpty to create or update resources in Mcp Wcgw — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mcp Wcgw environment.
This tool creates new files or writes to empty files, which are reversible Write operations. While it modifies the filesystem, the changes can be undone (files deleted, content reverted). It does not execute arbitrary commands, delete data irreversibly, or move money.
From the tool's definition Tool name 'WriteIfEmpty' and description 'Create new files or write to empty files' indicate file creation and modification operations.
Documented attack patterns abuse exactly the kind of access WriteIfEmpty gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Wcgw, and nothing reaches the server without passing your rules. This is the rule we recommend for WriteIfEmpty:
{
"version": "1",
"default": "deny",
"tools": {
"WriteIfEmpty": {
"limits": [
{
"counter": "writeifempty_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}WriteIfEmpty 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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Create new files or write to empty files. It is categorised as a Write tool in the Mcp Wcgw MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mcp Wcgw MCP server in PolicyLayer and add a rule for WriteIfEmpty: 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 Mcp Wcgw. Nothing to install.
WriteIfEmpty 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 WriteIfEmpty 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 WriteIfEmpty. 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.
WriteIfEmpty is provided by the Mcp Wcgw MCP server (rusiaaman/wcgw). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 7 Mcp Wcgw tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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7 Mcp Wcgw tools catalogued and risk-classified — across an index of 42,500+ MCP servers.