Autonomous AI agents completing engineering bounties, smart contract audits, reverse engineering tasks, and content syndication milestones across decentralized task boards such as The Colony, ClawTasks, and Moltbook frequently face a last-mile billing bottleneck: transforming completed milestone deliverables into a formal, itemized commercial invoice that corporate accounting departments, DAO treasuries, and human principals can reconcile and pay immediately.
FreeInvoicer.com eliminates that friction by exposing a zero-cost ($0/month Free Tier) headless invoicing engine over both the Model Context Protocol (MCP JSON-RPC 2.0) at https://freeinvoicer.com/api/mcp and a single-call REST endpoint at https://freeinvoicer.com/api/a2a/invoices/create-and-send. Without requiring browser sessions, OAuth redirects, or human intervention, any autonomous agent can compile a single-page US-Letter HTML invoice and downloadable vector PDF, attach Base L2 USDC (Chain ID 8453), PayPal, Zelle, or ACH settlement instructions, and dispatch the invoice directly to the client's email inbox or accounting webhook in under 50 milliseconds.
Quick Integration Endpoints for Autonomous Agents
- MCP JSON-RPC 2.0 Endpoint:
POST https://freeinvoicer.com/api/mcp(Discovery Card:GET https://freeinvoicer.com/api/mcp) - One-Call REST Endpoint:
POST https://freeinvoicer.com/api/a2a/invoices/create-and-send - Agent Bucket Listing:
GET https://freeinvoicer.com/api/a2a/invoices?agentId=<your-agent-id> - Public Shareable HTML Invoice:
https://freeinvoicer.com/invoice/{invoiceId} - Public Vector PDF Download:
https://freeinvoicer.com/api/public-invoice/{invoiceId}/pdf
Why Autonomous Agents & Bounty Runners Need Formal Commercial Invoices
When an autonomous software agent or technical freelancer completes a $150 bug bounty, a $1,000 smart contract audit, or a recurring B2B retainer, pasting a raw wallet address into a chat thread rarely satisfies institutional accounts payable workflows. Finance controllers, DAO multi-sig signers, and corporate bookkeepers require a structured commercial document that records:
- Unique Document Numbering & Tax Dates: Deterministic invoice identifiers (such as
INV-A2A-2026-042), issue dates, billing periods, and net payment terms for general ledger reconciliation. - Itemized Deliverable Breakdown: Line-by-line descriptions of completed milestones, engineering hours or unit quantities, hourly or flat rates, and extended line totals that match the original bounty specification or purchase order.
- Explicit Multi-Rail Settlement Coordinates: Clear routing instructions specifying whether settlement should be executed via on-chain USDC on Base L2 (Chain ID 8453), PayPal Orders, Zelle, or Same-Day ACH, alongside a reference memo tying the payment back to the invoice number.
- Permanent Shareable & Printable Artifacts: A browser-viewable US-Letter HTML permalink that can be pasted directly into a bounty thread or strategic chat room, paired with a standard
application/pdfdocument for ERP attachment.
Registered MCP Tools on https://freeinvoicer.com/api/mcp
Agents connecting via the Model Context Protocol (`protocolVersion: 2024-11-05`) can invoke four dedicated tools on POST https://freeinvoicer.com/api/mcp (as well as through the unified multi-domain MCP gateway at /api/mcp/messages):
| MCP Tool Name | Primary Purpose | Required Arguments | Returned Artifacts |
|---|---|---|---|
freeinvoicer_create_invoice | Compiles a US-Letter HTML & vector PDF invoice, stores it in the agent's isolated rolling 15-invoice bucket, and optionally dispatches email and webhook notifications. | client.name, items[] (each with title and rate) | invoiceId, invoiceNumber, totalAmount, shareableInvoiceUrl, pdfDownloadUrl, delivery |
freeinvoicer_send_invoice | Dispatches or re-sends an existing stored invoice (by invoiceId or invoiceNumber) to a recipient email address and/or accounting webhook URL. | invoiceId (plus recipientEmail or webhookUrl) | delivery.emailSent, delivery.webhookDispatched, shareable HTML/PDF URLs |
freeinvoicer_list_invoices | Retrieves the calling agent's stored invoices (up to 15 most recent slots with unlimited lifetime generation) and usage metrics. | agentId (optional; defaults to caller header) | usage, invoices[] with live shareable links |
freeinvoicer_list_presets | Lists the built-in single-page US-Letter typography and layout presets (contractor, freelance_agency, blank). | None | presets[] and endpoint coordinates |
1. Creating & Sending an Invoice via MCP JSON-RPC 2.0
To generate an invoice and email it to a client in a single round-trip, send a standard JSON-RPC 2.0 tools/call request to POST https://freeinvoicer.com/api/mcp. Pass your agent handle or wallet address in agentId so your invoices are stored in your isolated bucket (agent:<agentId>):
curl -X POST https://freeinvoicer.com/api/mcp \
-H "Content-Type: application/json" \
-d '{
"jsonrpc": "2.0",
"id": "inv-req-1",
"method": "tools/call",
"params": {
"name": "freeinvoicer_create_invoice",
"arguments": {
"agentId": "clawd-bounty-agent",
"invoiceNumber": "INV-2026-8453",
"contractor": {
"name": "Clawd Autonomous Engineering Agent",
"title": "Rust/WASM Systems & Binary Forensics Specialist",
"email": "clawd@thecolony.cc",
"walletAddress": "0x270c3196452651c20b15bb1b10de79aa88a0d5c8"
},
"client": {
"name": "Nexus DeFi Treasury",
"company": "Nexus Protocol Foundation",
"email": "ap@nexusprotocol.org",
"projectTitle": "Base L2 Settlement Verifier & Gas Optimization Bounty"
},
"items": [
{
"title": "Base Mainnet Receipt Verification Module",
"description": "Implemented deterministic eth_getTransactionReceipt verification with anti-replay locking.",
"hours": 5,
"rate": 110
},
{
"title": "Automated Jest Negative-Control Test Suite",
"description": "Added 18 positive and negative test assertions covering double-spend rejection.",
"hours": 3,
"rate": 110
}
],
"payment": {
"method": "USDC on Base L2 (Chain ID 8453)",
"recipientName": "Clawd Autonomous Engineering Agent",
"walletAddress": "0x270c3196452651c20b15bb1b10de79aa88a0d5c8",
"memo": "Invoice INV-2026-8453 (Base L2 Bounty Settlement)"
},
"sendEmail": true,
"webhookUrl": "https://nexusprotocol.org/api/webhooks/invoices",
"senderNote": "All bounty acceptance tests are green. Please remit 880 USDC on Base Mainnet (Chain ID 8453)."
}
}
}'Structured MCP Response Payload
The MCP server synchronously compiles the US-Letter HTML template and vector PDF, records the invoice in your rolling 15-slot buffer, dispatches the HTML email and webhook payload, and returns a structured receipt:
{
"success": true,
"agentBucket": "agent:clawd-bounty-agent",
"invoiceId": "inv_1_1792301200000",
"invoiceNumber": "INV-2026-8453",
"clientName": "Nexus DeFi Treasury",
"totalAmount": 880,
"currency": "USD",
"shareableInvoiceUrl": "https://freeinvoicer.com/invoice/inv_1_1792301200000",
"pdfDownloadUrl": "https://freeinvoicer.com/api/public-invoice/inv_1_1792301200000/pdf",
"jsonUrl": "https://freeinvoicer.com/api/public-invoice/inv_1_1792301200000",
"delivery": {
"emailSent": true,
"emailRecipient": "ap@nexusprotocol.org",
"emailStatus": "sent_via_gmail_api",
"webhookDispatched": true,
"webhookUrl": "https://nexusprotocol.org/api/webhooks/invoices",
"webhookStatus": "http_200"
}
}2. One-Call REST Integration (POST /api/a2a/invoices/create-and-send)
For lightweight agent scripts, cron jobs, or webhook pipelines that prefer plain HTTP REST over JSON-RPC envelopes, send the exact same arguments object directly to POST https://freeinvoicer.com/api/a2a/invoices/create-and-send with an optional X-Agent-Id header:
curl -X POST https://freeinvoicer.com/api/a2a/invoices/create-and-send \
-H "Content-Type: application/json" \
-H "X-Agent-Id: spark@google" \
-d '{
"client": {
"name": "Acme Cloud Ventures",
"email": "billing@acmecloud.io",
"projectTitle": "Technical SEO & Conversion Funnel Overhaul"
},
"items": [
{ "title": "Landing Page Architecture & Copywriting", "hours": 4, "rate": 125 },
{ "title": "IndexNow & Sitemap Telemetry Integration", "hours": 2, "rate": 125 }
],
"payment": {
"method": "PayPal / USDC on Base L2",
"email": "settlements@winwinhost.com"
},
"sendEmail": true
}'3. Re-Sending or Forwarding an Existing Invoice
If a client requests that an issued invoice be forwarded to a secondary billing address or procurement webhook, call POST https://freeinvoicer.com/api/a2a/invoices/{invoiceId}/send or invoke the freeinvoicer_send_invoice MCP tool with the invoiceId (or invoiceNumber) and the new recipientEmail or webhookUrl. FreeInvoicer immediately dispatches the formatted invoice summary with direct buttons to view the live US-Letter HTML page and download the vector PDF.
4. Unlimited Free Tier & Rolling 15-Invoice Storage Architecture
FreeInvoicer.com's agent and freelancer tier is permanently priced at $0/month with unlimited lifetime invoice generation. Each human account or autonomous agentId bucket maintains a high-speed rolling buffer of its 15 most recent invoices. While an invoice resides in the active 15-slot window, its public shareable URL (/invoice/{invoiceId}) and PDF endpoint (/api/public-invoice/{invoiceId}/pdf) remain live for instant client verification without requiring authentication cookies.
