Add invoice approvals to your software through an API.

Create an approval for an exact invoice and revision. The approver sees the supplier, amount, and supporting document. Fangst returns approve or reject to your system.

Contact See the API example

From API call to structured result.

Create the approvalSoftware or an AI agent supplies the exact subject and available decisions.
Share the URLThe approver sees what needs a decision and approves or rejects it.
Read the decisionFangst returns the recorded decision through the API or a signed webhook.

Continue your own invoice workflow after the decision.

Fangst supplies the hosted decision page and recorded result while your software keeps invoice processing and accounting integrations.

Create

POST https://api.fang.st/v1/approvals
Authorization: Bearer <FANGST_API_TOKEN>
Content-Type: application/json

{
  "title": "Approve invoice INV-1042",
  "subject": {
    "type": "invoice",
    "id": "INV-1042",
    "version": 1
  },
  "summary": {
    "supplier": "Northstar AS",
    "amount": 12450,
    "currency": "NOK"
  },
  "decisions": [
    "approve",
    "reject"
  ]
}

Completed result

{
  "status": "decided",
  "decision": "approved",
  "decided_at": "2026-09-14T12:30:00Z"
}

Use REST, MCP, polling, or webhooks.

Software uses the HTTP resources directly. Authorized AI agents can use the same API or intention-oriented Fangst MCP tools.

POST/v1/approvalsCreate an approval and receive its hosted URL.

GET/v1/approvals/:idRead the decision and its receipt.

POST/v1/approvals/:id/disableClose an approval link.

MCPrequest_human_approvalLet an authorized agent request a decision.

MCPget_human_approvalLet the agent read the decision.

Fangst runs the hosted interaction.

Hosted page

Responsive pages, clear sender context, validation, private or shared links, expiry, and submission limits.

Structured result

Typed values, authenticated file downloads, correlation metadata, timestamps, and stable response ids.

Reliable delivery

Polling, signed webhooks, retries with backoff, delivery history, idempotency, and replay.

Pay for completed interactions. No subscription.

Start with $1 free. Add funds from $10. Links, polling, webhooks, and abandoned requests do not use the main billable unit.

See pricing

Give your software a way to ask people.

Create the hosted interaction through Fangst and receive the structured result back.

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