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How to add guardrails for LLM-generated Cypher

To add guardrails for LLM-generated Cypher, guard the Neo4j driver with guard() from neo4j-guard.

Install​

pip install neo4j-guard

Guard the driver​

from neo4j import GraphDatabase
from neo4j_guard import GuardError, guard

driver = guard(GraphDatabase.driver(URL, auth=AUTH))

try:
    driver.execute_query("CREATE (:Person {name: 'Ada'})")
except GuardError as error:
    print(error)  # CREATE is not allowed in read mode

Return blocked queries to the LLM​

Catch GuardError in the tool that runs the LLM's queries and return the message. The message says what was blocked and why, so the LLM can rewrite the query.

from neo4j import GraphDatabase
from neo4j_guard import GuardError, guard

driver = guard(GraphDatabase.driver("neo4j://localhost:7687", auth=("neo4j", "password")))


def run_cypher(query: str) -> list[dict] | str:
    """Run a Cypher query and return its records, or why it was blocked."""
    try:
        records, _, _ = driver.execute_query(query)
    except GuardError as error:
        return f"Query blocked: {error}"
    return [record.data() for record in records]


print(run_cypher("MATCH (p:Person) DETACH DELETE p"))  # Query blocked: DELETE is not allowed in read mode