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 23 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

45.9/100 developing ▬ flat Agent 27/100 agent aware Heartbeat 100/100 alive Full breakdown ↓
scored 2026-11-13 · rubric v0.28.0 · Show this score on your site →

AccessFreemiumSelf serve⚡ Free to try

1 published contract 1 MCP Servers 2 Agent Skills

Invoicing Fintech Germany Small Business

Kin Score

Kin Score How this is scored →
scored 2026-11-13 · rubric v0.28.0

Composite quality — 45.9/100 · developing

Contract Quality 12.3 / 19

Developer Ergonomics 4.6 / 15

Access Clarity 9.3 / 15

Operational Transparency 0.5 / 10

Contract Governance 3.2 / 9

Discoverability 4.7 / 8

Regulatory Posture 2.8 / 15

Create-or-Update Ergonomics 0.0 / 10

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

MCP Tool Quality 6 / 6

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 applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented) Ask about this →
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0 Ask about this →
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented) Ask about this →
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link Ask about this →
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document Ask about this →
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented) Ask about this →

7 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Developer Ergonomics scores 30.4 — up to +13.9 composite points Ask about this →
Operational Transparency scores 4.8 — up to +12.4 composite points Ask about this →
Contract Quality scores 65.6 — up to +8.6 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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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 the provider profile at artifacts.apis.io/billingengine/apis.yml: open an issue on github.com/api-evangelist/billingengine to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 2

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

Model Context Protocol (MCP)

measured — observed by APIs.io (documented)

OpenAPI

measured — observed by APIs.io (published)

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

Agent Skills 2

Packaged agent skills for driving this provider's APIs from an AI assistant.

billingengine-create-invoice

AGENT SKILL

billingengine-record-and-list-payments

AGENT SKILL

BillingEngine API pricing

Prices published by BillingEngine, read 2026-10-19 from www.billingengine.com/de/pricing.

Plan	Price
Free	0,00 €
Basic	6,00 €
Premium	12,00 €

Plan details, limits and sources →

Pricing Plans 1

Published pricing tiers and plan structures.

BillingEngine Plans Pricing

3 plans

PLANS

Terms of Service 1

What its API terms permit and prohibit, quoted from its own page.

BillingEngine

5 quoted statements, read from BillingEngine's own page on 2026-11-09.

TERMS

Privacy & Data 1

Its role, the data it processes, retention and transfers, quoted from its own privacy page.

BillingEngine

24 quoted statements, read from BillingEngine's own page on 2026-11-09.

PRIVACY

Eligibility 1

Who may sign up and where, quoted from its own terms.

BillingEngine

2 quoted statements, read from BillingEngine's own page on 2026-11-09.

ELIGIBILITY

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. Counts are the severity each rule declares, not results of running them.

BillingEngine API Rules

17 rules · 15 error-severity 1 warn-severity 1 info-severity

SPECTRAL

JSON Schema 6

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

Customer

11 properties

JSON SCHEMA

InvoiceDetail

24 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 (API Evangelist recommendations) 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 5

Pricing, plans, and the legal terms of use

Plans

TermsOfService

PrivacyPolicy

Pricing

UsageTerms

Company 3

The organization behind the API

Newsroom

Newsroom

Blog

Blog

Website

Website

Other 5

Properties that don't map to a standard resource type

Hosts

Vendors

Leadership

DataProcessing

Eligibility

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)
accessModel:
  pricing: freemium
  onboarding: self-serve
  trial: false
  try_now: true
  public: false
  gated: none
  gated_source:
  - onboarding
  label: Freemium · Self-serve signup
  confidence: medium
  source:
  - plans
  - authentication
  - security
  generated: '2026-11-13'
  method: derived
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
- type: UsageTerms
  url: terms/billingengine-terms-of-service.yml
- type: DataProcessing
  url: privacy/billingengine-privacy-policy.yml
- type: Eligibility
  url: eligibility/billingengine-eligibility.yml
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-customer-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
- 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-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-enrichment:
  date: '2026-10-19'
  status: enriched
  artifacts_added: 23
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

BillingEngine API — frequently asked questions

Does BillingEngine have an API?

Yes. APIs.io lists 3 APIs from BillingEngine, including BillingEngine Customers API, BillingEngine Invoices API and BillingEngine Payments API.

Is there an OpenAPI specification for the BillingEngine API?

Yes. APIs.io indexes 3 OpenAPI specifications for BillingEngine, each linked for download from this page.

How do I authenticate with the BillingEngine API?

BillingEngine uses bearer-token authentication (http · 1 scheme). The details are profiled on APIs.io as BillingEngine Authentication.

How much does the BillingEngine API cost?

BillingEngine publishes its prices; its Free plan is 0,00 € as of 2026-10-19. APIs.io lists 3 pricing plans for BillingEngine, with each plan's price, limits and inclusions under Pricing on this page.

Does BillingEngine have an MCP server?

Yes. APIs.io lists 1 MCP server for BillingEngine.

Is the BillingEngine API ready for AI agents?

BillingEngine has a Kin Score of 45.9 out of 100 (developing) and an Agent Readiness score of 26.6 (agent-aware), scored by API Evangelist on 2026-11-13.

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One button, every client — Claude, Cursor, VS Code and the rest.

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