Connect Invoiced to ChatGPT: Automate Billing and Customer Accounts

If you want to connect Invoiced to ChatGPT so your AI agents can execute billing operations, track accounts receivable (AR), sweep metered charges, and manage subscriptions, you need a Model Context Protocol (MCP) server. This infrastructure layer translates natural language intent from an LLM into the structured, authenticated REST requests required by the Invoiced API.

If your team uses Claude, check out our guide on connecting Invoiced to Claude or explore our broader architectural overview on connecting Invoiced to AI Agents.

Giving a Large Language Model (LLM) read and write access to a core financial system like Invoiced is a high-stakes engineering challenge. You must handle complex, nested JSON payloads for line items and taxes, manage payment tokens securely, and deal with strict financial state machines. You either spend weeks building and maintaining custom MCP proxy infrastructure, or you use a managed platform like Truto to dynamically generate a secure, authenticated MCP server URL.

This guide breaks down exactly how to use Truto to generate an MCP server for Invoiced, connect it natively to ChatGPT, and execute complex billing workflows.

Stop writing boilerplate API integration code. Let Truto generate secure, managed MCP servers for your AI agents in seconds. :::

The Engineering Reality of the Invoiced API

Building an MCP server is essentially building a custom API gateway. While the open MCP standard provides a reliable way for ChatGPT to discover tools, executing those tools against Invoiced introduces several domain-specific API challenges.

If you decide to build a custom MCP server for Invoiced, your engineering team owns these specific integration hurdles:

Strict Financial State Machines

Invoiced enforces a strict state machine across its core objects. For example, you cannot consolidate invoices for a customer unless they actually have open invoices and the consolidation flag is enabled. You cannot refund a charge (create_a_invoiced_refund) for an amount exceeding the original capture, or apply a credit balance adjustment without specifying the exact currency tied to the customer. When an LLM generates a request, your server must gracefully handle these 422 Unprocessable Entity errors and map them back to the LLM so it can correct its next attempt.

Polymorphic Payment Sourcing

When executing manual payment charges via create_a_invoiced_charge, the API requires exactly one payment source. However, this source can arrive in three different formats: a payment_source_id, an invoiced_token, or a gateway_token. A generic MCP implementation will often confuse an LLM into passing multiple mutually exclusive tokens at once. Your tool definitions must clearly delineate these parameters using strict JSON Schema validation.

Strict Pass-Through of Rate Limits

When operating agents at scale, hitting API limits is inevitable. It is critical to understand that Truto does not retry, throttle, or apply backoff on rate limit errors. When the upstream Invoiced API returns an HTTP 429 error, Truto passes that error directly to the caller. Truto normalizes the upstream rate limit information into standardized headers (ratelimit-limit, ratelimit-remaining, ratelimit-reset) following the IETF spec. The caller - in this case, your agent orchestration layer or custom client - is entirely responsible for handling retry logic and backoff. Do not assume the integration layer will absorb 429s for you.

Step 1: Generating the Invoiced MCP Server

Truto creates MCP tools dynamically based on documentation-driven schema parsing. Each server is scoped to a single authenticated instance of Invoiced. You can create this server in two ways.

Method 1: Via the Truto UI

If you are setting up an internal agent and prefer a visual interface:

1. Navigate to the Integrated Accounts page in the Truto dashboard.
2. Select your connected Invoiced account.
3. Click the MCP Servers tab.
4. Click Create MCP Server.
5. Select your desired configuration. You can filter by methods (e.g., only read operations) or tags (e.g., only invoices and customers).
6. Copy the generated MCP server URL. It will look like https://api.truto.one/mcp/<hashed-token>.

Method 2: Via the Truto API

For production workflows, you should programmatically generate short-lived or tightly scoped MCP servers for your AI agents.

Make a POST request to the /integrated-account/:id/mcp endpoint:

curl -X POST https://api.truto.one/integrated-account/$INTEGRATED_ACCOUNT_ID/mcp \
  -H "Authorization: Bearer $TRUTO_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "ChatGPT Billing Agent",
    "config": {
      "methods": ["read", "write", "custom"],
      "tags": ["invoices", "customers", "payments"]
    }
  }'

The response returns a secure URL that acts as both the endpoint and the authentication token for the MCP connection:

{
  "id": "mcp-xyz-789",
  "name": "ChatGPT Billing Agent",
  "config": {
    "methods": ["read", "write", "custom"],
    "tags": ["invoices", "customers", "payments"]
  },
  "expires_at": null,
  "url": "https://api.truto.one/mcp/a1b2c3d4e5f6..."
}

Treat this URL as a secret. It provides direct, authenticated access to the Invoiced API for the specified account.

Step 2: Connecting the MCP Server to ChatGPT

With your MCP URL in hand, you must register the server with your ChatGPT environment. You can do this via the UI for standard usage, or via a configuration file if you are running custom developer agents.

Method A: Via the ChatGPT UI

If you are on a ChatGPT Pro, Plus, Business, Enterprise, or Education plan with Developer mode enabled:

1. In ChatGPT, click your profile and navigate to Settings -> Apps -> Advanced settings.
2. Ensure Developer mode is toggled on.
3. Under MCP servers / Custom connectors, click Add new.
4. Enter a name (e.g., "Invoiced Billing").
5. Paste the Truto MCP URL into the Server URL field.
6. Click Add and save your settings.

ChatGPT will immediately ping the endpoint, execute a handshake, and ingest the tool schemas available on that Invoiced account.

Method B: Via Manual Configuration File (SSE Transport)

If you are building headless agents or using a local inspector, you can configure the MCP connection using the Server-Sent Events (SSE) transport configuration.

Create your MCP configuration file (e.g., mcp-config.json):

{
  "mcpServers": {
    "invoiced": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-sse",
        "--url",
        "https://api.truto.one/mcp/a1b2c3d4e5f6..."
      ]
    }
  }
}

This instructs the MCP client to route JSON-RPC traffic directly to the Truto edge endpoint, which then proxies the execution to Invoiced.

Invoiced Hero Tools for AI Agents

When you connect Invoiced through Truto, the LLM discovers dozens of potential API methods. To build effective billing agents, focus on these high-leverage hero tools.

1. create_a_invoiced_invoice

Description: Generates a new invoice for a specific customer, complete with line items, taxes, discounts, and shipping details.

Usage Notes: The LLM must pass an array of items in the request body. If the customer already has unbilled pending line items, consider using the trigger tool instead to avoid duplicating charges.

"Draft a new invoice for customer ID 9876 with two line items: 'Annual Subscription' for $1,200 and 'Implementation Fee' for $500. Set the due date to 30 days from today."

2. invoiced_customers_get_balance

Description: Retrieves a customer's current credit balance, balance history, and amount outstanding.

Usage Notes: This is the most efficient way for an agent to check AR status. It returns available_credits, past_due, and total_outstanding in a single payload, preventing the need to paginate through all open invoices.

"Check the outstanding balance for customer ID 1234. If they have a past-due amount, let me know how much it is."

3. invoiced_invoices_send_email

Description: Sends an invoice to a customer via email.

Usage Notes: You can optionally override the default invoice template by supplying custom subject and message strings. It returns the delivery state and open count.

"Email invoice INV-5543 to the primary contact on file. Include a custom message asking them to update their payment method."

4. invoiced_invoices_pay

Description: Triggers a manual charge attempt on an invoice's default payment source.

Usage Notes: This bypasses the standard automatic collection schedule. If the charge fails, Invoiced will return an error detailing the decline reason. The returned object updates the paid flag and attempt_count.

"Attempt to charge the default credit card on file for invoice INV-9988 right now."

5. create_a_invoiced_subscription

Description: Creates a recurring billing subscription linking a customer to a plan, optionally including addons, taxes, and contract renewal settings.

Usage Notes: Requires a valid customer ID and plan ID. You can preview a subscription first to calculate the MRR and first invoice amount before committing it to the database.

"Start a new 'Enterprise Tier' subscription (Plan ID 44) for customer ID 8832 starting on the 1st of next month."

6. invoiced_pending_line_items_trigger_invoice

Description: Triggers an invoice generation that sweeps up all of a customer's unbilled pending line items.

Usage Notes: Crucial for metered billing. If your application pushes usage events to Invoiced as pending line items throughout the month, this tool consolidates them into a single bill.

"Sweep all pending usage charges for customer ID 455 into a new invoice."

Note: To see the complete list of available operations, required fields, and JSON schemas, view the Invoiced integration page.

Workflows in Action

Connecting an LLM directly to financial tools unlocks powerful agentic workflows. Instead of writing custom scripts to handle common billing operations, ChatGPT can execute multi-step processes autonomously.

Workflow 1: AR Follow-up and Collection

Account management teams spend hours chasing down failed payments. An AI agent can check a customer's balance, attempt to collect, and escalate if necessary.

"Look up the balance for Acme Corp (ID 551). If they are past due, attempt to charge their default payment method for the open invoice. If the charge fails, email them the invoice with a reminder to update their card."

Execution Steps:

1. invoiced_customers_get_balance: The agent checks the customer's AR state, noting a past_due balance of $4,500 tied to an open invoice.
2. invoiced_invoices_pay: The agent triggers a manual payment attempt for the invoice ID found in the balance check.
3. invoiced_invoices_send_email: The payment attempt returns an error (e.g., insufficient funds). The agent catches this and immediately triggers the email tool with a customized reminder message.

sequenceDiagram
    participant User as User
    participant Agent as AI Agent
    participant Truto as Truto MCP
    participant Invoiced as Invoiced API

    User->>Agent: Check balance & collect for ID 551
    Agent->>Truto: Call invoiced_customers_get_balance(551)
    Truto->>Invoiced: GET /customers/551/balance
    Invoiced-->>Truto: Returns past_due: 4500
    Truto-->>Agent: JSON Result
    Agent->>Truto: Call invoiced_invoices_pay(INV-123)
    Truto->>Invoiced: POST /invoices/INV-123/pay
    Invoiced-->>Truto: 422 Payment Declined
    Truto-->>Agent: Error Details
    Agent->>Truto: Call invoiced_invoices_send_email(INV-123)
    Truto->>Invoiced: POST /invoices/INV-123/emails
    Invoiced-->>Truto: Email queued
    Truto-->>Agent: Success
    Agent-->>User: Payment failed. Reminder email sent.

Workflow 2: Metered Billing Sweep

If you bill customers based on usage (e.g., API calls, storage), you can instruct the agent to orchestrate the end-of-month billing cycle.

"We just finished the billing cycle. Add a $50 overage fee as a pending line item for customer ID 899, then trigger their invoice to sweep all pending charges and send it out via email."

Execution Steps:

1. create_a_invoiced_pending_line_item: The agent creates a $50 line item attached to the customer.
2. invoiced_pending_line_items_trigger_invoice: The agent sweeps the new overage charge, plus any existing unbilled usage, into a fresh invoice.
3. invoiced_invoices_send_email: The agent reads the newly generated invoice ID and dispatches it to the customer's billing contact.

Security and Access Control

Giving an LLM the ability to void invoices or trigger credit card charges requires strict guardrails. Truto's MCP implementation allows you to lock down the server before handing it to ChatGPT.

• Method Filtering: Constrain the MCP server to specific operation types. Set methods: ["read"] to ensure the agent can only check balances and view invoices, but never create charges or subscriptions.
• Tag Filtering: Limit the surface area by functional group. Set tags: ["invoices", "customers"] to hide access to sensitive endpoints like payment_sources or credit_notes.
• Additional Authentication Layer: For internal tooling, set require_api_token_auth: true. This forces ChatGPT (or any custom client) to provide a valid Truto API token in addition to possessing the MCP URL, ensuring only authorized team members can execute tools.
• Automated Expiration: Set an expires_at timestamp. Once the timestamp passes, the server URL is automatically destroyed - perfect for temporary agent sessions or one-off billing audits.

Wrapping Up

Connecting Invoiced to ChatGPT transforms a static financial ledger into a dynamic, agentic system. By using a managed MCP server, you eliminate the need to write custom schema parsers, maintain complex integration state, or deal with pagination logic.

Instead of losing engineering cycles to API maintenance, your team can focus on orchestrating sophisticated billing workflows through natural language.

Stop writing boilerplate API integration code. Let Truto generate secure, managed MCP servers for your AI agents in seconds. :::