AI agents call list_spaces to retrieve information from NebulaGraph MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a read-only operation that enumerates available graph spaces in NebulaGraph. It retrieves information without modifying, deleting, or executing arbitrary operations. The blast radius of misuse is minimal since it only exposes schema/metadata that an authenticated user would typically have access to.
From the tool's definition Tool name is 'list_spaces' and description states it 'List all available spaces' — a query operation that retrieves metadata about database spaces with no side effects.
Documented attack patterns abuse exactly the kind of access list_spaces gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and NebulaGraph MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_spaces:
{
"version": "1",
"default": "deny",
"tools": {
"list_spaces": {}
}
}list_spaces is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all available spaces. It is categorised as a Read tool in the NebulaGraph MCP Server MCP Server, which means it retrieves data without modifying state.
Register the NebulaGraph MCP Server MCP server in PolicyLayer and add a rule for list_spaces: 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 NebulaGraph MCP Server. Nothing to install.
list_spaces 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 list_spaces 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 list_spaces. 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.
list_spaces is provided by the NebulaGraph MCP Server MCP server (nebula-contrib/nebulagraph-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from NebulaGraph MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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5 NebulaGraph MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.