k_nearest_neighbors · Neo4j Gds MCP: Risk & Policy

WHAT IT DOES

What k_nearest_neighbors does on Neo4j Gds

AI agents use k_nearest_neighbors to create or update resources in Neo4j Gds — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Neo4j Gds environment.

WHY IT NEEDS A POLICY

Why k_nearest_neighbors needs a policy

The tool explicitly creates new relationships in the graph database as part of its operation. This is a write operation that modifies the graph structure by adding edges, which is reversible (relationships can be deleted) but does persistently alter the database state.

From the tool's definition creates new relationships between each node and its k nearest neighbors

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

k_nearest_neighbors Rate-limited

k_nearest_neighbors 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "k_nearest_neighbors": {
      "limits": [
        {
          "counter": "k_nearest_neighbors_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Neo4j Gds, so you can run agents against it safely.

FAQ

Questions about k_nearest_neighbors

What does the k_nearest_neighbors tool do? +

The K-Nearest Neighbors algorithm computes a distance value for all node pairs in the graph and creates new relationships between each node and its k nearest neighbors. It is categorised as a Write tool in the Neo4j Gds MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on k_nearest_neighbors? +

Register the Neo4j Gds MCP server in PolicyLayer and add a rule for k_nearest_neighbors: 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 Neo4j Gds. Nothing to install.

What risk level is k_nearest_neighbors? +

k_nearest_neighbors is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit k_nearest_neighbors? +

Yes. Add a rate_limit block to the k_nearest_neighbors 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.

How do I block k_nearest_neighbors completely? +

Set action: deny in the PolicyLayer policy for k_nearest_neighbors. 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.

What MCP server provides k_nearest_neighbors? +

k_nearest_neighbors is provided by the Neo4j Gds MCP server (neo4j-contrib/gds-agent). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.