Calculate distance between geometries (requires PostGIS extension)
AI agents call geo_distance to retrieve information from Postgres Mcp Legacy without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a read-only geospatial calculation. It computes distances between geometric objects but does not create, modify, delete, or execute arbitrary operations on the database. The output is a calculated value with no side effects. Even if misused by an AI agent, it can only read and compute; it cannot alter state or trigger external operations.
From the tool's definition Tool name 'geo_distance' and description 'Calculate distance between geometries' indicate a query/calculation operation that retrieves computed results without modifying data.
Documented attack patterns abuse exactly the kind of access geo_distance 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_distance:
{
"version": "1",
"default": "deny",
"tools": {
"geo_distance": {}
}
}geo_distance is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Calculate distance between geometries (requires PostGIS extension). It is categorised as a Read tool in the Postgres Mcp Legacy MCP Server, which means it retrieves data without modifying state.
Register the Postgres Mcp Legacy MCP server in PolicyLayer and add a rule for geo_distance: 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_distance 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 geo_distance 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_distance. 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_distance 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.