"create_invoice" tool always returned "Failed to create invoice"

[dangkhoa0303]

Describe the bug

Hi,
I'm integrating Stripe MCP into my agent. I've tested the 'create_invoice' tool and noticed that it always returned an error with the message "Failed to create invoice". I checked the logs and the parameters the agent passed to the MCP tool are as follows:
[
{
"tool_name": "create_invoice",
"Tool_Parameters": {
"customer": "cus_Si6SJRAgyxHHui"
}
}
]

I tested with HTTP request tool and used only the "customer" parameter. Also, in another workflow of mine where the agent used the http request tool to create an invoice, it worked just fine.

I only had this issue when using MCP. Could you please have a look into this?

Thank you very much.

To Reproduce

1. MCP Tool description: Use this tool to create a Stripe invoice.
2. Prompt to the agent: Create an invoice for customer with id cus_Si6SJRAgyxHHui.
3. Agent's response: I attempted to create an invoice for the customer with ID cus_Si6SJRAgyxHHui, but the operation failed with a "Failed to create invoice" error.

Expected behavior

The MCP tool should be executed successfully.

Code snippets

OS

macOS

Language version

n8n MCP Client

Library version

Latest as of 13th August 2025

API version

Latest as of 13th August 2025

Additional context

No response

[dangkhoa0303]

UPDATE:

Below is the schema of the "create_invoice" tool. "days_until_due" is NOT required. However, if the agent omits this field in the request and only uses the "customer" field, the request will fail with "Failed to create invoice".

The request will only be successful when both fields "customer" and "days_until_due" are used. Please fix this discrepancy.

{
  "name": "create_invoice",
  "description": "\n  This tool will create an invoice in Stripe.\n  \n  It takes two arguments:\n  - customer (str): The ID of the customer to create the invoice for.\n\n  - days_until_due (int, optional): The number of days until the invoice is due.\n  ",
  "schema": {
    "type": "object",
    "properties": {
      "customer": {
        "type": "string",
        "description": "The ID of the customer to create the invoice for."
      },
      "days_until_due": {
        "type": "integer",
        "description": "The number of days until the invoice is due."
      }
    },
    "required": [
      "customer"
    ],
    "additionalProperties": false,
    "$schema": "http://json-schema.org/draft-07/schema#"
  }
}

[matv-stripe]

@dangkhoa0303 do you see this error when using the remote MCP server? https://docs.stripe.com/mcp