A calculator that was dynamically loaded
AI agents invoke bonus_calculator to trigger actions in MCP TypeScript Starter. 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.
The description is largely uninformative ('A calculator that was dynamically loaded'). The dynamic loading aspect raises the severity above a simple Read/Write tool, as dynamically loaded tools can execute arbitrary logic. However, a 'calculator' at face value is a Read/compute operation.
From the tool's definition 'A calculator that was dynamically loaded' — the tool was dynamically loaded (via sibling tool 'load_bonus_tool'), suggesting runtime code loading behaviour
Documented attack patterns abuse exactly the kind of access bonus_calculator gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP TypeScript Starter, and nothing reaches the server without passing your rules. This is the rule we recommend for bonus_calculator:
{
"version": "1",
"default": "deny",
"tools": {
"bonus_calculator": {
"limits": [
{
"counter": "bonus_calculator_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}bonus_calculator 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.
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A calculator that was dynamically loaded. It is categorised as a Execute tool in the MCP TypeScript Starter MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the MCP TypeScript Starter MCP server in PolicyLayer and add a rule for bonus_calculator: 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 MCP TypeScript Starter. Nothing to install.
bonus_calculator is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the bonus_calculator 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 bonus_calculator. 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.
bonus_calculator is provided by the MCP TypeScript Starter MCP server (sammorrowdrums/mcp-typescript-starter). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP TypeScript Starter, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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8 MCP TypeScript Starter tools catalogued and risk-classified — across an index of 43,000+ MCP servers.