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fastbill

Work with FastBill invoices, customers, payments, reminders, and e-invoice exports through the FastBill XML API.

Skill by HybridAIOne

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Install

Works with Claude Code, Claude apps, Codex, Cursor, Gemini CLI, GitHub Copilot, VS Code, OpenCode, Goose, Windsurf. Read the repository before you give any tool access to your data.

npx agentmarket install skill/hybridaione-fastbill

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About

Work with FastBill invoices, customers, payments, reminders, and e-invoice exports through the FastBill XML API.

Use cases: backend, finance

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Permissions

What this skill can do and what it asks for, from its SKILL.md. Checked Oct 25, 2026.

Tools
No tools found
Secrets
None asked for
Install scripts
None found

Network hosts it talks to 1

  • codeload.github.com · found in install command

Files it touches

  • ~/.claude/skills/fastbill

What's inside

Skill name
fastbill
Description
Work with FastBill invoices, customers, payments, reminders, and e-invoice exports through the FastBill XML API.
License
MIT
Instructions
118 lines in SKILL.md · view on GitHub

Before installing

  • Ships executable scripts

Files (5)

  • SKILL.md
  • scenarios.json · evals/
  • fastbill.cjs
  • index.cjs
  • operator-setup.md · references/

SKILL.md (first lines)

# FastBill

Use this skill for FastBill invoices, customers, payments, reminders, and
document metadata. The helper wraps concrete FastBill API services: it
serializes JSON-shaped inputs to XML and parses XML responses.

## Core Rules

- Use the helper plus built-in `http_request` for live API calls. Do not use
  `curl`, ad hoc `node -e`, `grep`, or shell parsing for FastBill.
- FastBill API URL: `https://my.fastbill.com/api/1.0/api.php`.
  The `/api/1.0/` prefix is only for secret-route matching.
- Basic auth is injected by the gateway from `FASTBILL_BASIC_AUTH`. Never print,
  build, or ask for the FastBill API key.
- Writes require explicit operator intent and `--operator-grant`. Prefer
  `--dry-run` when converting free text, CSV, or time tracking into invoice data.
- Prefer invoice IDs for writes. If multiple invoices/customers match, ask for
  the exact ID before writing.
- If unsure about a service or field, check `https://apidocs.fastbill.com`.

## Commands

Show commands:

```bash
node skills/fastbill/fastbill.cjs --help
```

Build an `http_request` payload for the built-in `http_request` tool:

```bash
node skills/fastbill/fastbill.cjs http-request invoice.get --filter-json '{"INVOICE_ID":"123"}'
node skills/fastbill/fastbill.cjs http-request customer.create --data-json '{"CUSTOMER_TYPE":"business","ORGANIZATION":"Acme GmbH","COUNTRY_CODE":"DE"}' --operator-grant
```

Parse a saved `http_request` response wrapper/body:

```bash
node skills/fastbill/fastbill.cjs parse-response --body-file /tmp/fastbill-response.json
```

Direct helper network calls are only for operator-controlled shell tests with a
valid gateway token already exported:

```bash
node skills/fastbill/fastbill.cjs request invoice.get --filter-json '{"INVOICE_ID":"123"}'
```

Common invoice payloads:

```bash
node skills/fastbill/fastbill.cjs http-request invoice.get --filter-json '{"END_DUE_DATE":"2026-04-08"}' --limit 100
node skills/fastbill/fastbill.cjs http-request invoice.create --data-json '{"CUSTOMER_ID":"123","INVOICE_TITLE":"Consulting Januar - Juni 2026","ITEMS":{"ITEM":[{"DESCRIPTION":"Consulting","QUANTITY":"8","UNIT_PRICE":"120.00","VAT_PERCENT":"19"}]}}' --operator-grant
node skills/fastbill/fastbill.cjs http-request invoice.update --data-json '{"INVOICE_ID":"456","INVOICE_TITLE":"YouGov SVOD Januar - Juni 2026"}' --operator-grant
node skills/fastbill/fastbill.cjs http-request invoice.setpaid --data-json '{"INVOICE_ID":"456","PAID_DATE":"2026-05-07","PAYMENT_METHOD":"bank transfer"}' --operator-grant
node skills/fastbill/fastbill.cjs http-request invoice.sendbyemail --data-json '{"INVOICE_ID":"456","RECIPIENT":{"TO":"billing@example.com"},"SUBJECT":"Payment reminder","MESSAGE":"Please review the outstanding invoice and payment status."}' --operator-grant
```

## Clone / Copy Invoice

FastBill's API does not expose a dedicated invoice clone/copy service, even
though the UI has one. Implement clone as `invoice.get` then `invoice.create`.

1. Use one targeted `invoice.get`; prefer date, customer/project text, title,
   and service-period terms over broad account-wide searches.
2. Select one source invoice. If ambiguous, ask for the invoice ID.
3. Copy relevant source fields: `CUSTOMER_ID`, `CUSTOMER_COSTCENTER_ID`,
   `CONTACT_ID`, `CURRENCY_CODE`, `TEMPLATE_ID`/`TEMPLATE_HASH`, `INTROTEXT`,
   `INVOICE_TITLE`, references, discounts, VAT settings, and `ITEMS`.
4. Omit lifecycle/source fields: `INVOICE_ID`, `INVOICE_NUMBER`, `STATE`,
   `PAID_DATE`, `PAYMENTS`, `DOCUMENT_URL`, `DETAILS_URL`, totals, and
   cancellation flags.
5. Apply requested changes, then create the draft with
   `invoice.create --operator-grant`. Extra reads need a concrete missing field.

## Invoice Title Fields

- Invoice title field: `INVOICE_TITLE` in `invoice.create` and
  `invoice.update`. Do not use `TITLE`, `NAME`, or `SUBJECT`.
- Existing draft title edit: `invoice.update` with `INVOICE_ID` and
  `INVOICE_TITLE`.
- `INTROTEXT` is intro/body text before line items.
- `ITEMS.ITEM[].DESCRIPTION` is line-item text.
- `SUBJECT` is only for email actions such as `invoice.sendbyemail`.
- Do not set `INVOICE_NUMBER` when creating or editing a draft title.

## Write Services

These require `--operator-grant`: `customer.create/update/delete`,
`contact.create/update/delete`, `invoice.create/update/delete/complete/cancel/lock/sendbyemail/sendbypost/setpaid`,
`estimate.create/delete/sendbyemail/createinvoice`, `article.create/update/delete`,
`recurring.create/update/delete`, `revenue.create/setpaid/delete`,
`expense.create`, `project.create/update/delete`, `time.create/update/delete`,
and `document.create`, `webhook.create/delete`.

## Errors

- Gateway 401 mentioning `WEB_API_TOKEN` or `GATEWAY_API_TOKEN`: the request did
  not reach FastBill; use built-in `http_request` in normal runtime.
- Missing/forbidden secret route: fix `FASTBILL_BASIC_AUTH` or its route.
- FastBill 401 with `Wrong API KEY` / credentials: the route worked, but
  FastBill rejected the stored Basic credential.

## References

- Operator setup and API notes: [references/operator-setup.md](references/operator-setup.md)

## Validation

Run:

```bash
python3 skills/skill-creator/scripts/quick_validate.py skills/fastbill
node skills/fastbill/fastbill.cjs --help
node skills/fastbill/fastbill.cjs http-request invoice.get --filter-json '{"INVOICE_ID":"123"}'
node skills/fastbill/fastbill.cjs request invoice.get --filter-json '{"INVOICE_ID":"123"}' --dry-run
```

From HybridAIOne/hybridclaw, MIT.

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    From GitHub (fetched Oct 24, 2026).

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    fastbill skill. Agent Mart. https://agentmart.dev/skills/hybridaione-fastbill (last updated 2026-10-24)