Apply surgical text replacements to files. Best for small changes (<20% of file size).
AI agents use edit_block to create or update resources in Desktop Commander MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Desktop Commander MCP environment.
This tool creates or modifies file data in a reversible manner—text can be edited and changed back. While the capability is powerful on a local system (high severity due to potential to modify critical configs, code, or credentials), it remains Write-category since edits are not inherently irreversible.
From the tool's definition Tool description states 'Apply surgical text replacements to files', indicating it modifies file content. The server context confirms it provides 'advanced file operations' for editing files.
Documented attack patterns abuse exactly the kind of access edit_block gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Desktop Commander MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for edit_block:
{
"version": "1",
"default": "deny",
"tools": {
"edit_block": {
"limits": [
{
"counter": "edit_block_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}edit_block 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.
Free to start. No card required.
Apply surgical text replacements to files. Best for small changes (<20% of file size). It is categorised as a Write tool in the Desktop Commander MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Desktop Commander MCP server in PolicyLayer and add a rule for edit_block: 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 Desktop Commander MCP. Nothing to install.
edit_block 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 edit_block 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 edit_block. 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.
edit_block is provided by the Desktop Commander MCP server (mrgnss/claudedesktopcommander). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Desktop Commander MCP, 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.
19 Desktop Commander MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.