neo4j.create_constraint · Neo4j MCP Server MCP

WHAT IT DOES

What neo4j.create_constraint does on Neo4j MCP Server

AI agents use neo4j.create_constraint to create or update resources in Neo4j MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Neo4j MCP Server environment.

WHY IT NEEDS A POLICY

Why neo4j.create_constraint needs a policy

Creating a constraint modifies the database schema in a reversible manner—constraints can be dropped or altered. This is a write operation that affects data integrity rules but does not delete data or execute arbitrary code. The high severity reflects that improper constraints could impact data validation and application behavior, but the change is reversible, distinguishing it from destructive operations.

From the tool's definition Tool name 'create_constraint' and description 'Create a constraint on a node label' indicate data structure modification. Constraints are schema-level modifications that alter database rules and validation logic.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

neo4j.create_constraint Rate-limited

neo4j.create_constraint 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": {
    "neo4j.create_constraint": {
      "limits": [
        {
          "counter": "neo4j.create_constraint_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 MCP Server, so you can run agents against it safely.

FAQ

Questions about neo4j.create_constraint

What does the neo4j.create_constraint tool do? +

Create a constraint on a node label. It is categorised as a Write tool in the Neo4j MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on neo4j.create_constraint? +

Register the Neo4j MCP Server MCP server in PolicyLayer and add a rule for neo4j.create_constraint: 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 MCP Server. Nothing to install.

What risk level is neo4j.create_constraint? +

neo4j.create_constraint is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit neo4j.create_constraint? +

Yes. Add a rate_limit block to the neo4j.create_constraint 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 neo4j.create_constraint completely? +

Set action: deny in the PolicyLayer policy for neo4j.create_constraint. 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 neo4j.create_constraint? +

neo4j.create_constraint is provided by the Neo4j MCP Server MCP server (vpro1032/neo4j-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.