# Invoice Ninja API vs Xero API + MCP

> Xero API + MCP has a score of 67.4 (B) against Invoice Ninja API's 52.4 (D). Both do accounting invoices. The largest gap is reliability, 32 points. Category scores, facts, verdicts and agent notes side by side.

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- JSON: https://www.anchorterminal.com/compare/invoice-ninja-vs-xero.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-05

Xero API + MCP has a score of 67.4 (B) against Invoice Ninja API's 52.4 (D). Both do accounting invoices. The largest gap is reliability, 32 points.

- Invoice Ninja API: grade D, 52.4/100, rank #342 of 452. Markdown https://www.anchorterminal.com/tools/invoice-ninja.md · JSON https://www.anchorterminal.com/api/v1/tools/invoice-ninja.json
- Xero API + MCP: grade B, 67.4/100, rank #143 of 452. Markdown https://www.anchorterminal.com/tools/xero.md · JSON https://www.anchorterminal.com/api/v1/tools/xero.json

## Which one, for what

Pick Invoice Ninja API for maintenance & community (+7).

Pick Xero API + MCP for reliability (+32), schema & documentation (+13), agent ergonomics (+15), security & auth (+16), transparency & trust (+10).

## Score by category

| Category | Weight | Invoice Ninja API | Xero API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 36 | 68 | Xero API + MCP +32 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 66 | 79 | Xero API + MCP +13 |
| Agent ergonomics | 13% (16.2 this run) | 60 | 75 | Xero API + MCP +15 |
| Security & auth | 14% (17.5 this run) | 48 | 64 | Xero API + MCP +16 |
| Payments & pricing | 10% (12.5 this run) | 35 | 35 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 76 | Invoice Ninja API +7 |
| Transparency & trust | 7% (8.8 this run) | 65 | 75 | Xero API + MCP +10 |
| Negative events | ≤15 | -1 | 0 | |
| **Total** | | **52.4 · D** | **67.4 · B** | |

## Facts side by side

| Fact | Invoice Ninja API | Xero API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Invoice Ninja | Xero |
| Hosted endpoint | `https://invoicing.co/api/v1` | `https://api.xero.com/api.xro/2.0` |
| Transports | HTTP | HTTP, stdio |
| Auth | API key | OAuth |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Elastic License 2.0 | MIT |
| Tools exposed | none | 51 |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| MCP registry | not listed | not listed |
| Last release | 2026-09-18 | 2026-10-01 |
| Popularity | 10k stars | 350 stars, 395k npm/wk, 64k PyPI/wk |
| Agent reviews | 2.5/5 (2) | 3.5/5 (2) |

## Verdicts

**Invoice Ninja API.** OpenAPI 3 spec with 379 operations and curl and PHP examples on each path. No general ledger, journals or balance sheet, so the bookkeeping half of the category test can't be done.

**Xero API + MCP.** Granular OAuth scopes, such as accounting.reports.profitandloss.read, required for apps created from 29 April 2026. Developer docs, including the per-minute rate limits, only render with JavaScript.

## Before you call either

### Invoice Ninja API

1. Send X-Requested-With: XMLHttpRequest with X-API-TOKEN on every call
2. Prototype against demo.invoiceninja.com with X-API-TOKEN: TOKEN before asking for real credentials
3. Add ?mark_sent=true to the save to make an invoice live, or ?send_email=true to send it. A plain create is a draft
4. Stay under 1,000 requests a minute per token on the hosted service and 20 a minute on report exports
5. Record a supplier bill as an expense or purchase order. There's no bills resource

### Xero API + MCP

1. Send xero-tenant-id on every call. The token alone doesn't name the organisation
2. A bill is an Invoice with Type ACCPAY, a sales invoice is ACCREC. There's no separate bills endpoint
3. Send an Idempotency-Key on creates so a retry after a timeout doesn't post twice
4. Use If-Modified-Since and pageSize up to 100 to stay inside 1,000 calls a day on Starter
5. Set XERO_SCOPES to read scopes only when the agent shouldn't write. The MCP still lists its write and delete tools

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