AI agents call expand_node to retrieve information from Ariadne without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and queries structural information about microservice dependencies and topology without executing commands, modifying data, or causing side effects. It is purely informational/exploratory, consistent with Read category operations like 'list' and 'get'.
From the tool's definition Tool name 'expand_node' and description 'One-hop neighbours of a known node' indicates retrieval of graph structure information without modification or execution.
Attacks that exploit this kind of access
One-hop neighbours of a known node (endpoint / Kafka topic /. It is categorised as a Read tool in the Ariadne MCP Server, which means it retrieves data without modifying state.
Register the Ariadne MCP server in PolicyLayer and add a rule for expand_node: 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 Ariadne. Nothing to install.
expand_node 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 expand_node 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 expand_node. 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.
expand_node is provided by the Ariadne MCP server (whyy9527/ariadne). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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