xero_add_line_item_to_bill · Xero Expenses MCP

WHAT IT DOES

What xero_add_line_item_to_bill does on Xero Expenses MCP

AI agents use xero_add_line_item_to_bill to create or update resources in Xero Expenses MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Xero Expenses MCP environment.

WHY IT NEEDS A POLICY

Why xero_add_line_item_to_bill needs a policy

This tool modifies existing bills/invoices by adding line items, which changes the financial amounts and obligations recorded in the accounting system. While reversible (it's a Write operation, not Destructive), the high severity reflects the financial impact: adding incorrect line items to bills could misrepresent company finances, create false payment obligations, or inflate invoices.

From the tool's definition Tool description states 'Add a line item to an existing DRAFT bill' — this modifies an existing bill by appending financial line items.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

xero_add_line_item_to_bill Rate-limited

xero_add_line_item_to_bill 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "xero_add_line_item_to_bill": {
      "limits": [
        {
          "counter": "xero_add_line_item_to_bill_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about xero_add_line_item_to_bill

What does the xero_add_line_item_to_bill tool do? +

Add a line item to an existing DRAFT bill or invoice. Supports both flat amount (amount) and quantity × unit price (quantity + unitPrice). NOTE: Keep ≤9 line items per bill due to Xero. It is categorised as a Write tool in the Xero Expenses MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on xero_add_line_item_to_bill? +

Register the Xero Expenses MCP server in PolicyLayer and add a rule for xero_add_line_item_to_bill: 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 Xero Expenses MCP. Nothing to install.

What risk level is xero_add_line_item_to_bill? +

xero_add_line_item_to_bill is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit xero_add_line_item_to_bill? +

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

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

xero_add_line_item_to_bill is provided by the Xero Expenses MCP server (muness/xero-expenses-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.