AI agents use fill_selection to create or update resources in Gimp — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Gimp environment.
The tool modifies image data (writes/paints into a selection), which is reversible and typical of image editing operations. It does not delete data (ruling out Destructive), does not execute arbitrary code (Execute), and has no financial impact.
From the tool's definition Tool name 'fill_selection' combined with server description stating it 'exposes GIMP's full PyGObject API for AI-powered image manipulation.' Fill operations modify image data by applying color/pattern to selected regions, creating reversible changes to the…
Documented attack patterns abuse exactly the kind of access fill_selection gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Gimp, and nothing reaches the server without passing your rules. This is the rule we recommend for fill_selection:
{
"version": "1",
"default": "deny",
"tools": {
"fill_selection": {
"limits": [
{
"counter": "fill_selection_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fill_selection 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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fill_selection. It is categorised as a Write tool in the Gimp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Gimp MCP server in PolicyLayer and add a rule for fill_selection: 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 Gimp. Nothing to install.
fill_selection 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 fill_selection 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 fill_selection. 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.
fill_selection is provided by the Gimp MCP server (maorcc/gimp-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Gimp, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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79 Gimp tools catalogued and risk-classified — across an index of 43,000+ MCP servers.