Add a relationship edge between two nodes
AI agents use add_edge to create or update resources in CodeRAG — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your CodeRAG environment.
The tool creates new data (edges/relationships) in the knowledge graph in a reversible manner. It does not delete, execute code, or move data. The severity is medium because while it modifies the graph structure, the impact is limited to adding metadata relationships about code structure rather than changing code itself or causing destructive effects.
From the tool's definition Tool name 'add_edge' and description 'Add a relationship edge between two nodes' indicate creation of new relationships in the Neo4J knowledge graph. This is a write operation that modifies the graph structure by creating connections between existing entities.
Documented attack patterns abuse exactly the kind of access add_edge gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and CodeRAG, and nothing reaches the server without passing your rules. This is the rule we recommend for add_edge:
{
"version": "1",
"default": "deny",
"tools": {
"add_edge": {
"limits": [
{
"counter": "add_edge_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_edge 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.
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Add a relationship edge between two nodes. It is categorised as a Write tool in the CodeRAG MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the CodeRAG MCP server in PolicyLayer and add a rule for add_edge: 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 CodeRAG. Nothing to install.
add_edge is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add_edge 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 add_edge. 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.
add_edge is provided by the CodeRAG MCP server (jonnoc/coderag). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from CodeRAG, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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