BillingEngine

BillingEngine provides online invoicing software tailored for freelancers and small businesses in Germany. Its REST API enables listing, creating, and updating customers and draft invoices, recording payments, and downloading invoices as PDF or XML e‑invoices (ZUGFeRD / XRechnung, EN 16931). The platform also offers an MCP server for AI assistants, requiring an API key from a paid plan.

BillingEngine publishes 3 API contracts indexed on the APIs.io network: Customers API, Invoices API, and Payments API. Tagged areas include Invoicing, Fintech, Germany, and Small Business.

The BillingEngine catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

BillingEngine’s developer surface includes support, pricing, engineering blog, authentication, documentation, and 20 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

47.2/100 developing Agent 27/100 agent aware Full breakdown ↓
scored 2026-10-23 · rubric v0.25.0 · Show this score on your site →

1 published contract 1 MCP Servers

Invoicing Fintech Germany Small Business

Kin Score

Kin Score How this is scored →
scored 2026-10-23 · rubric v0.25.0

Composite quality — 47.2/100 · developing

Contract Quality 13.9 / 21

Developer Ergonomics 5.2 / 17

Access Clarity 10.7 / 17

Operational Transparency 0.6 / 11

Contract Governance 3.6 / 10

Discoverability 4.8 / 9

Regulatory Posture 3.7 / 15

Agent readiness — 27/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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<a href="https://apis.io/providers/billingengine/"><img src="https://apis.io/badge/billingengine/card.svg" alt="BillingEngine on APIs.io — Kin Score by API Evangelist"></a>

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Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/billingengine: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 3

Individual APIs this provider publishes, each with its own machine-readable definition.

BillingEngine Customers API

Customers of the account.

BillingEngine Invoices API

Invoices, created as drafts, and their PDF and XML e-invoice downloads.

BillingEngine Payments API

Payments received for sent invoices.

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

BillingEngine MCP Server

MCP SERVER

Pricing Plans 1

Published pricing tiers and plan structures.

Billingengine Plans Pricing

3 plans

PLANS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Billingengine Context

12 classes · 53 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

BillingEngine API Rules

17 rules · 15 errors 1 warnings 1 info

SPECTRAL

JSON Schema 6

Standalone JSON Schema definitions for this provider's data models.

Customer

11 properties

JSON SCHEMA

InvoiceDetail

0 properties

JSON SCHEMA

InvoiceInput

9 properties

JSON SCHEMA

Invoice

16 properties

JSON SCHEMA

PaymentInput

4 properties

JSON SCHEMA

Payment

9 properties

JSON SCHEMA

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Billingengine Authentication

http · 1 scheme

SECURITY

Billingengine Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Billingengine Agentic Access

12 operations · 5 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgentSkill

LLMsTxt

MCPServer

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

DataModel

ErrorCatalog

Conformance

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Access & Security 2

Authentication, authorization, and security posture

Authentication

Authentication

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 4

Pricing, plans, and the legal terms of use

Plans

TermsOfService

PrivacyPolicy

Pricing

Company 3

The organization behind the API

Newsroom

Newsroom

Blog

Blog

Website

Website

Other 3

Properties that don't map to a standard resource type

Hosts

Hosts

Vendors

Vendors

Leadership

Leadership

Source (apis.yml)

aid: billingengine
name: BillingEngine
description: BillingEngine provides online invoicing software tailored for freelancers and small businesses in Germany. Its
  REST API enables listing, creating, and updating customers and draft invoices, recording payments, and downloading invoices
  as PDF or XML e‑invoices (ZUGFeRD / XRechnung, EN 16931). The platform also offers an MCP server for AI assistants, requiring
  an API key from a paid plan.
url: https://raw.githubusercontent.com/api-evangelist/billingengine/refs/heads/main/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-19 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-19'
modified: '2026-10-19'
tags:
- Invoicing
- Fintech
- Germany
- Small Business
tags_raw:
- invoicing
- fintech
- api
- germany
- small-business
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: AgenticAccess
  url: agentic-access/billingengine-agentic-access.yml
- type: Plans
  url: plans/billingengine-plans-pricing.yml
- type: Spectral
  url: rules/billingengine-rules.yml
- type: JSONLD
  url: json-ld/billingengine-context.jsonld
- type: Vocabulary
  url: vocabulary/billingengine-vocabulary.yml
- type: AgentSkill
  url: skills/_index.yml
- type: DataModel
  url: data-model/billingengine-data-model.yml
- type: ErrorCatalog
  url: errors/billingengine-problem-types.yml
- type: Conformance
  url: conformance/billingengine-conformance.yml
- type: LLMsTxt
  url: llms/billingengine-llms.txt
- type: MCPServer
  url: mcp/billingengine-mcp.yml
- type: Hosts
  url: hosts/billingengine-hosts.yml
- type: Vendors
  url: vendors/billingengine-vendors.yml
- type: TermsOfService
  url: https://www.billingengine.com/de/terms_of_service
- type: Support
  url: https://www.billingengine.com/de/help
- type: PrivacyPolicy
  url: https://www.billingengine.com/de/privacy_notice
- type: Pricing
  url: https://www.billingengine.com/de/pricing
- type: Newsroom
  url: https://www.billingengine.com/de/news
- type: Leadership
  url: https://www.billingengine.com/de/team
- type: Blog
  url: https://www.billingengine.com/de/blog
- type: GitHubOrganization
  url: https://github.com/billingengine
- type: Authentication
  url: authentication/billingengine-authentication.yml
- type: DomainSecurity
  url: security/billingengine-domain-security.yml
- type: Website
  url: https://www.billingengine.com/
- type: Documentation
  url: https://www.billingengine.com/en/api
apis:
- aid: billingengine:billingengine-customers-api
  name: BillingEngine Customers API
  description: Customers of the account.
  humanURL: https://www.billingengine.com/en/api
  baseURL: https://www.billingengine.com/api/v1
  tags:
  - Customers
  properties:
  - type: OpenAPI
    url: openapi/billingengine-customers-api-openapi.yml
  - type: JSONSchema
    url: json-schema/billingengine-invoice-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-invoice-input-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-invoice-detail-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-customer-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-payment-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-payment-input-schema.json
- aid: billingengine:billingengine-invoices-api
  name: BillingEngine Invoices API
  description: Invoices, created as drafts, and their PDF and XML e-invoice downloads.
  humanURL: https://www.billingengine.com/en/api
  baseURL: https://www.billingengine.com/api/v1
  tags:
  - Invoices
  properties:
  - type: OpenAPI
    url: openapi/billingengine-invoices-api-openapi.yml
  - type: JSONSchema
    url: json-schema/billingengine-invoice-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-invoice-input-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-invoice-detail-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-customer-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-payment-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-payment-input-schema.json
- aid: billingengine:billingengine-payments-api
  name: BillingEngine Payments API
  description: Payments received for sent invoices.
  humanURL: https://www.billingengine.com/en/api
  baseURL: https://www.billingengine.com/api/v1
  tags:
  - Payments
  properties:
  - type: OpenAPI
    url: openapi/billingengine-payments-api-openapi.yml
  - type: JSONSchema
    url: json-schema/billingengine-invoice-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-invoice-input-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-invoice-detail-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-customer-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-payment-schema.json
  - type: JSONSchema
    url: json-schema/billingengine-payment-input-schema.json
x-submission-notes: 'What does it do?

  BillingEngine is online invoicing software for freelancers and small businesses in Germany. The REST API lets you list,
  create and change customers and draft invoices, record payments, and download invoices as PDF or as an XML e-invoice (ZUGFeRD
  / XRechnung, EN 16931). The MCP server (billingengine-mcp) exposes the same functions to AI assistants such as Claude and
  Cursor. It cannot delete anything and sends nothing to customers. Both need an API key from a paid plan.


  Who maint'
x-submission-probe: OpenAPI 3.1 200, apis.json 200, soft-404 clean
x-submitted-by: press@billingengine.com (apis.io/add, 2026-10-19)
x-enrichment:
  date: '2026-10-19'
  status: enriched
  artifacts_added: 23
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

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