create_kernel · Cellrank MCP: Risk & Policy

WHAT IT DOES

What create_kernel does on Cellrank

AI agents invoke create_kernel to trigger actions in Cellrank. 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 IT NEEDS A POLICY

Why create_kernel needs a policy

Creating a CellRank kernel involves running computational operations to initialize and configure a kernel object for trajectory analysis. This is an Execute-level action as it triggers external computation within the CellRank library framework, rather than simply reading data or writing a persistent record.

From the tool's definition Create a CellRank kernel based on the specified type and parameters

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_kernel Rate-limited

create_kernel 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_kernel": {
      "limits": [
        {
          "counter": "create_kernel_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Cellrank, so you can run agents against it safely.

FAQ

Questions about create_kernel

What does the create_kernel tool do? +

Create a CellRank kernel based on the specified type and parameters. It is categorised as a Execute tool in the Cellrank MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on create_kernel? +

Register the Cellrank MCP server in PolicyLayer and add a rule for create_kernel: 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 Cellrank. Nothing to install.

What risk level is create_kernel? +

create_kernel is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit create_kernel? +

Yes. Add a rate_limit block to the create_kernel 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.

How do I block create_kernel completely? +

Set action: deny in the PolicyLayer policy for create_kernel. 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.

What MCP server provides create_kernel? +

create_kernel is provided by the Cellrank MCP server (scmcphub/cellrank-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.