This record as markdown: /tools/io-github-devopam-mcpg/run-cypher.md
What run_cypher does on Mcpg
AI agents invoke run_cypher to trigger actions in Mcpg. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
Why run_cypher is rated High
Despite the empty description, the tool name 'run_cypher' indicates code/query execution capability. This falls under Execute rather than Read because Cypher queries can perform writes, deletes, and complex operations beyond simple retrieval. Severity is high due to potential for data modification or unauthorized access in a production PostgreSQL environment.
From the tool's definition Tool named 'run_cypher' with empty description on PostgreSQL MCP server. Cypher is a query language for graph databases (Neo4j).
Attacks that exploit this kind of access
The rule that runs run_cypher safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Mcpg, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For run_cypher, this is the rule to start with:
run_cypher stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Mcpg, apply this rule, and every run_cypher call is checked against it from then on.
Questions about run_cypher
run_cypher is a execute tool on the Mcpg MCP server. It is categorised as a Execute tool in the Mcpg MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Mcpg MCP server in PolicyLayer and add a rule for run_cypher: 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 Mcpg. Nothing to install.
run_cypher is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the run_cypher 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 run_cypher. 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.
run_cypher is provided by the Mcpg MCP server (pypi:mcpg). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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