companion_up · Yaver MCP: Risk & Policy

WHAT IT DOES

What companion_up does on Yaver

AI agents invoke companion_up to trigger actions in Yaver. 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.

PARAMETERS

Parameter	Type	Required	Description
`repo`	string	Yes	Absolute path to the serverless project repo

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why companion_up needs a policy

companion_up triggers real processes with real consequences. An agent gone sideways doesn't fire it once — it starts dozens of builds, sends mass notifications, or burns through compute before anyone looks up.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

companion_up Rate-limited

companion_up 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": {
    "companion_up": {
      "limits": [
        {
          "counter": "companion_up_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 Yaver, so you can run agents against it safely.

FAQ

Questions about companion_up

What does the companion_up tool do? +

Arm the companion manifest (yaver.companion.yaml) at repo: schedule HTTP crons on the in-process scheduler and start/instal durable workers as OS units. Idempotent. Reboot-durable. It is categorised as a Execute tool in the Yaver MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

What parameters does companion_up accept? +

companion_up accepts 1 parameter: repo. Required: repo. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on companion_up? +

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

What risk level is companion_up? +

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

Can I rate-limit companion_up? +

Yes. Add a rate_limit block to the companion_up 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 companion_up completely? +

Set action: deny in the PolicyLayer policy for companion_up. 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 companion_up? +

companion_up is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.