Reads two shapefiles directly, concatenates them vertically.
AI agents call append_gpd to retrieve information from GIS MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool reads two shapefiles and concatenates them, which is fundamentally a read/query operation producing a combined result. There is no indication it writes or modifies any files on disk; it appears to return the concatenated data in memory. Confidence is slightly reduced because 'append' in the name could imply a write side-effect, but the description only mentions reading and concatenating, not saving.
From the tool's definition Reads two shapefiles directly, concatenates them vertically
Documented attack patterns abuse exactly the kind of access append_gpd gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and GIS MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for append_gpd:
{
"version": "1",
"default": "deny",
"tools": {
"append_gpd": {}
}
}append_gpd is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Reads two shapefiles directly, concatenates them vertically. It is categorised as a Read tool in the GIS MCP Server MCP Server, which means it retrieves data without modifying state.
Register the GIS MCP Server MCP server in PolicyLayer and add a rule for append_gpd: 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 GIS MCP Server. Nothing to install.
append_gpd is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the append_gpd 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 append_gpd. 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.
append_gpd is provided by the GIS MCP Server MCP server (mahdin75/gis-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from GIS MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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98 GIS MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.