Create buffer zones around geometries (requires PostGIS)
AI agents use geo_buffer to create or update resources in Postgres Mcp Legacy — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Postgres Mcp Legacy environment.
This tool creates new geometric buffer features in the spatial database, which is a reversible modification operation. While it doesn't delete data, it does generate and persist new geometry objects. The severity is medium because misuse could fill the database with unintended spatial data, but the operation is reversible (the created buffers can be deleted).
From the tool's definition Tool 'geo_buffer' performs spatial geometry operations that create new buffer zones around geometries using PostGIS. The verb 'create' and the action of generating new geometric data indicates a write operation that modifies or adds data to the database.
Documented attack patterns abuse exactly the kind of access geo_buffer gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Postgres Mcp Legacy, and nothing reaches the server without passing your rules. This is the rule we recommend for geo_buffer:
{
"version": "1",
"default": "deny",
"tools": {
"geo_buffer": {
"limits": [
{
"counter": "geo_buffer_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}geo_buffer 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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Create buffer zones around geometries (requires PostGIS). It is categorised as a Write tool in the Postgres Mcp Legacy MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Postgres Mcp Legacy MCP server in PolicyLayer and add a rule for geo_buffer: 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 Postgres Mcp Legacy. Nothing to install.
geo_buffer 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 geo_buffer 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 geo_buffer. 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.
geo_buffer is provided by the Postgres Mcp Legacy MCP server (neverinfamous/postgres-mcp-legacy). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Postgres Mcp Legacy, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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60 Postgres Mcp Legacy tools catalogued and risk-classified — across an index of 43,000+ MCP servers.