AI agents use replace_docstring to create or update resources in Ast Editor — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ast Editor environment.
This tool modifies existing docstrings in source code, which is a Write operation: it changes file content but is reversible (the old docstring can be restored). It does not delete code irreversibly (not Destructive), does not execute arbitrary commands (not Execute), and does not involve financial transactions (not Financial).
From the tool's definition Tool name 'replace_docstring' indicates modification of documentation strings within code files. The server description emphasizes surgical file editing via AST, and sibling tools (add_cell, add_field, add_method, etc.) are all Write operations that create or…
Documented attack patterns abuse exactly the kind of access replace_docstring gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Ast Editor, and nothing reaches the server without passing your rules. This is the rule we recommend for replace_docstring:
{
"version": "1",
"default": "deny",
"tools": {
"replace_docstring": {
"limits": [
{
"counter": "replace_docstring_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}replace_docstring 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_docstring. It is categorised as a Write tool in the Ast Editor MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Ast Editor MCP server in PolicyLayer and add a rule for replace_docstring: 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 Ast Editor. Nothing to install.
replace_docstring 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 replace_docstring 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 replace_docstring. 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.
replace_docstring is provided by the Ast Editor MCP server (kambleakash0/agent-skills). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Ast Editor, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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59 Ast Editor tools catalogued and risk-classified — across an index of 43,000+ MCP servers.