Invoicing you can script, subscribe to, and hand to an agent
A REST API for invoices, clients and remittance advice, signed webhooks for the events that matter, and an MCP server with 81 tools, all behind one API key.
01 / API & Webhooks
What is the Invoice My Clients API?
The API is the programmable side of your account. With a Bearer key you can list and create invoices and clients, manage remittance advice, and trigger an e-invoice send, from your own code, Zapier or Make. Outbound webhooks push events to your endpoint the moment something changes.
The same key unlocks the MCP server, so Claude, an IDE or any Model Context Protocol client can use the full tool set: invoices, clients, proposals, purchase orders, time tracking and more. Keys are created under Settings, then Developer, with an optional expiry of up to 365 days.
- REST v1 endpoints for invoices, clients and remittance advice.
- 25 webhook events with HMAC-SHA256 signatures and retries.
- MCP server with 81 tools over streamable HTTP.
- Keys prefixed imc_live_, hashed at rest, revocable at any time.
02 / Capabilities
Built for automation, not just integrations
The API covers the objects an automation actually touches, and the webhooks tell you when to act.
API keys
Generate keys in Settings under Developer. Each key shows once, is stored as a hash, can carry an expiry, and can be revoked without touching the others.
Webhooks
Subscribe an HTTPS endpoint to any of 25 events across invoices, payments, clients, remittance advice and recurring invoices, or to everything with a wildcard.
MCP server
Connect at https://mcp.invoicemyclients.com/mcp with your key and an AI client gets 81 tools, from creating an invoice to logging time and sending a proposal.
Signed and retried
Every delivery carries X-Webhook-Event, X-Webhook-Timestamp and an HMAC-SHA256 X-Webhook-Signature. Failed deliveries retry after 5 and 25 seconds and are logged for inspection.
Rate limits
The MCP server allows 300 requests per minute per client. Key creation is limited to five keys per minute per account.
Developer docs in the app
The Developer section in Settings documents each endpoint with curl examples and the MCP connection snippet for Claude Desktop and Claude Code.
03 / Process
How to connect
Create an API key
In Settings, open Developer and generate a key. Copy it now: only a masked version is shown afterwards.
Call the REST API
Send requests with Authorization: Bearer imc_live_... to /v1/invoices, /v1/clients or /v1/remittance-advice. Create, list, update and send from your own code or an automation platform.
Register a webhook
Add your HTTPS endpoint and pick the events. Verify the HMAC signature on receipt and respond within 10 seconds.
Point an AI client at the MCP server
Paste the mcpServers snippet from the Developer section into Claude Desktop, or run claude mcp add with the HTTP transport, and the tools are live.
04 / FAQ
API FAQs
Which resources does the REST API cover?
Invoices (list, create, send as e-invoice), clients (list, create) and remittance advice (list, create, update, send). Payments, proposals and time entries are available through the MCP server tools.
Which webhook events can I subscribe to?
Twenty-five events in five groups: invoice (created, sent, viewed, paid, overdue and more), payment (initiated, succeeded, failed, recorded), client (created, updated), remittance advice (created, sent, acknowledged) and recurring invoices. A wildcard subscribes to all of them.
How are webhooks secured?
Each request is signed with HMAC-SHA256 over the timestamp and body using your endpoint secret, sent in the X-Webhook-Signature header alongside the event name and timestamp. Deliveries that fail are retried and logged.
Which plans include API access?
API keys, webhooks and the MCP server are part of the Business plan and above. Enterprise and White Label plans add pooled AI allowances and, on White Label, embed rights.
Is there a Zapier or Make integration?
The REST API was built with Zapier and Make in mind and works with their HTTP modules today. Native apps in both directories are in beta; ask support for access.
Ship your first integration this afternoon
One key for the REST API, webhooks and the MCP server.
No credit card required to start.