set_tool_tier · Fusebase MCP Server MCP: Risk & Policy

WHAT IT DOES

What set_tool_tier does on Fusebase MCP Server

AI agents invoke set_tool_tier to trigger actions in Fusebase MCP Server. 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 set_tool_tier needs a policy

This tool modifies the active session state by enabling additional tools, which is an execution of a configuration/state change rather than a simple read or data write. It affects the operational environment for subsequent actions, potentially expanding the attack surface by unlocking additional capabilities.

From the tool's definition 'Enable extended Fusebase tools for this session' — triggers a runtime configuration change that alters which tools are available for the current session

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_tool_tier Rate-limited

set_tool_tier 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": {
    "set_tool_tier": {
      "limits": [
        {
          "counter": "set_tool_tier_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 Fusebase MCP Server, so you can run agents against it safely.

FAQ

Questions about set_tool_tier

What does the set_tool_tier tool do? +

Enable extended Fusebase tools for this session. By default only core tools (23) are loaded for performance. Call this with tier. It is categorised as a Execute tool in the Fusebase MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on set_tool_tier? +

Register the Fusebase MCP Server MCP server in PolicyLayer and add a rule for set_tool_tier: 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 Fusebase MCP Server. Nothing to install.

What risk level is set_tool_tier? +

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

Can I rate-limit set_tool_tier? +

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

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

set_tool_tier is provided by the Fusebase MCP Server MCP server (ryan-haver/fusebase-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.