Paste bytes to file with append/insert/replace modes
AI agents use buffer_paste to create or update resources in Clippy — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Clippy environment.
This tool creates or modifies file content reversibly through paste operations with multiple modes (append/insert/replace). It does not permanently delete data (ruling out Destructive) and does not execute arbitrary code (ruling out Execute).
From the tool's definition Tool name 'buffer_paste' and description 'Paste bytes to file with append/insert/replace modes' explicitly indicates the ability to modify files through append, insert, and replace operations.
Documented attack patterns abuse exactly the kind of access buffer_paste gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Clippy, and nothing reaches the server without passing your rules. This is the rule we recommend for buffer_paste:
{
"version": "1",
"default": "deny",
"tools": {
"buffer_paste": {
"limits": [
{
"counter": "buffer_paste_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}buffer_paste 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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Paste bytes to file with append/insert/replace modes. It is categorised as a Write tool in the Clippy MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Clippy MCP server in PolicyLayer and add a rule for buffer_paste: 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 Clippy. Nothing to install.
buffer_paste 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 buffer_paste 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 buffer_paste. 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.
buffer_paste is provided by the Clippy MCP server (neilberkman/clippy). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Clippy, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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7 Clippy tools catalogued and risk-classified — across an index of 43,000+ MCP servers.