Register an external MCP server as a data backend. Creates a data_connector project if project_id is not provided. Credentials are never stored — only env var names are saved.
AI agents use crow_register_backend to create or update resources in Crow — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Crow environment.
This tool creates new project entities and registers backend connectors, which are reversible modifications to the system state. While it involves configuration of external systems and credential handling (via env var references), the primary action is creating/writing a new data connector project.
From the tool's definition Tool description states it 'Register[s] an external MCP server as a data backend' and 'Creates a data_connector project' — both are write operations that create or register new entities.
Documented attack patterns abuse exactly the kind of access crow_register_backend gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Crow, and nothing reaches the server without passing your rules. This is the rule we recommend for crow_register_backend:
{
"version": "1",
"default": "deny",
"tools": {
"crow_register_backend": {
"limits": [
{
"counter": "crow_register_backend_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}crow_register_backend 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.
Free to start. No card required.
Register an external MCP server as a data backend. Creates a data_connector project if project_id is not provided. Credentials are never stored — only env var names are saved. It is categorised as a Write tool in the Crow MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Crow MCP server in PolicyLayer and add a rule for crow_register_backend: 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 Crow. Nothing to install.
crow_register_backend 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 crow_register_backend 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 crow_register_backend. 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.
crow_register_backend is provided by the Crow MCP server (kh0pper/crow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Crow, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
576 Crow tools catalogued and risk-classified — across an index of 43,000+ MCP servers.