Ranked by the provider's API Evangelist rating — the Kin Score is scored per provider, not per API, so every API of a provider shares its band. How the rating works →

Exemplar 3 Complete, well-documented, and agent-ready

Stax APIThe Stax REST API (published as "stax-api") exposes 133 operations across 101 paths at https://apiprod.fatt...75.3 Candid Health Patient Collections APIManage patient invoicing, payments, refunds, and accounts receivable. Automates patient billing workflows a...68.8 Telr QuickLink and E-Invoicing APIRemote creation of QuickLink payment links and e-invoices with extra data fields, for merchants who collect...67.5

Strong 5 Solid coverage with minor gaps

Visma Bookkeeping & Invoicing / eAccounting APIREST API for Bookkeeping & Invoicing / eAccounting (Spiris, formerly Visma Spcs) covering customers, suppli...61.9 HyperPay HyperBillHyperBill issues invoices and shareable payment links that collect payment through the HyperPay platform wi...60.6 Flywire Invoicing APIREST API for the Flywire Invoicing Platform — contacts, invoices, credit notes and invoice payments for a c...60.1 Pabbly Subscription Billing APIREST API for Pabbly Subscription Billing — 95 documented operations across customers, subscriptions, produc...57.5 Autopay Accounting APIThe Autopay Accounting API provides Autopay invoicing data to external accounting and ERP systems, enabling...56.3

Developing 14 Usable, with meaningful gaps to close

Zoho InvoiceThe Zoho Invoice API allows you to perform all the operations that you do with the web client. It is built ...54.1 AdvicePay APIThe AdvicePay REST API (v1.0.1) exposes the fee-for-service billing platform to integrators: admins, adviso...53.3 AccountsIQ Integration API 2.0The current AIQ SOAP 1.1 integration web service. 219 operations covering customers, suppliers, stock items...53.1 Coupa Invoicing APIThe Coupa Invoicing API provides RESTful endpoints for creating, updating, and querying invoices associated...51.9 Semble Billing & Payments APIGraphQL surface for practice finances — invoices, invoice payments and line items, account statements, prod...51.9 Proactis Invoice APIRetrieve invoices from Proactis, receive them pushed to your own endpoint as they reach a configured status...51.4 Tabs Platform APIREST API for the Tabs revenue automation platform that exposes the core data model of customers, contracts,...50.8 Agree APIREST API for the Agree contract-to-cash platform. 56 operations across six resources: Agreements (create fr...50.3 Spotnana Invoicing APIAPIs to manage invoicing.48.8 Deskera Books APIREST API for Deskera Books, the cloud ERP and accounting product — contacts, products, accounts, invoices, ...48.7 bp Open Fleet Invoice Management APIReal-time access to fleet invoice data. GET /invoices retrieves and searches invoices with cost breakdowns,...48.6 Request Finance AP and AR APIThe Accounts Payable and Receivable REST API for issuing invoices, accepting crypto and fiat payments, runn...45.8 GuestReady Invoicing APIThe invoicing API from GuestReady — 2 operation(s) for invoicing.42.4 Depositphotos Enterprise APIThe Enterprise API provides organizations with full content licensing workflows including searching 331M+ a...42.3

Thin 32 Limited public surface area

Billogram v2 APIRESTful JSON API for managing invoices (billograms), customers, items, credit invoices, payment sources, of...39.1 CyberSource Invoicing APICreates and manages payment invoices with customizable fields, due dates, and customer information. Generat...38.1 FreeAgent REST APIRESTful API for the FreeAgent cloud accounting platform. Provides full access to invoices, estimates, conta...38.1 Outpost Merchant of Record APIREST API to issue proforma invoices for B2B customers paying by bank transfer, receive settlement webhooks,...37.5 Wave Financial GraphQL APIGraphQL API providing programmatic access to Wave accounting features including businesses, customers, invo...37.5 Hnry Platform APIThe REST API behind the Hnry app. It backs the Hnry iOS/Android clients and the published Hnry Zapier integ...37.3 Bakuraku APIREST API for the Bakuraku (バクラク) back-office suite. Publicly documented capabilities are retrieval and list...37.0 National Australia Bank (NAB) Gateway Payments APINAB's first-party merchant payments REST API platform (the NAB Gateway / NAB Transact developer portal at n...36.2 UNFI EDI IntegrationUNFI supports Electronic Data Interchange (EDI) for automated exchanges of purchase orders, invoices, and f...35.9 Cora APICora's transactional banking API for Direct Integration: registered boleto and carnê (installment) issuance...35.5 Fatora REST APIFatora's REST API for hosted-checkout payment collection, card tokenization, refunds and payment verificati...35.3 upGrad Partner Service APIChannel-partner operations API for upGrad's referral and franchise network: partner onboarding and KYC docu...35.3 MyFatoorah Invoicing APICreate invoices and payment links.34.3 Zenskar APIZenskar's REST API for billing, contracts, usage metering, invoicing, payments, credit notes, and accountin...34.1 Harvest API v2REST API for managing clients, projects, tasks, time entries, expenses, invoices, estimates, and users in H...34.0 Taulia Supplier APIThe supplier-side integration API described in the SAP Taulia Description of Software Services. It exchange...33.4 MakeLeaps APIREST API for the MakeLeaps cloud invoicing platform. Authenticated with OAuth 2.0 client-credentials agains...33.3 FreshBooks REST APIREST API for FreshBooks providing CRUD access to clients, invoices, estimates, expenses, projects, time ent...32.2 FreshBooks Webhooks (Callbacks API)Event delivery surface for the FreshBooks Callbacks API. Subscribers register an HTTPS endpoint, complete a...32.2 Oyster HR APIREST API for global employment operations including hiring, payroll, benefits, time off, expenses, invoicin...32.0 Geidea Pay by Invoice APICreate, update, fetch, delete, and send payment invoices (KSA) that customers settle through a Geidea-hoste...31.8 Geidea Pay by Link APIProgrammatically create, update, fetch, delete, and send (by email or SMS) shareable payment links so custo...31.8 Clear Books REST APIRESTful API for integrating with Clear Books accounting software to manage invoices, payments, contacts, ba...29.8 NYISO Finance Invoicing APIThe Invoicing component of NYISO's Finance APIs, retrieving daily reconciliation data for both settlements ...29.6 Holded Invoicing APIThe Invoicing API from Holded — 15 operation(s) for invoicing.28.9 Holded REST APIREST API for managing invoicing, contacts, products, accounting, projects, employees, and CRM records insid...28.9 Cegid Click & Finance APIREST API for the Koalaboox / Cegid Click & Finance invoicing and invoice-financing platform. Resource-orien...28.8 Exact Online REST / OData APIREST and OData API (v1) for Exact Online covering financials, sales, purchasing, inventory, HRM, CRM, proje...28.5 Iugu APIRESTful API providing 140+ endpoints for payment processing, customer management, invoicing, subscriptions,...27.9 Zoho Invoice APIREST API for managing organizations, contacts, items, invoices, estimates, credit notes, recurring invoices...27.8 Accelo REST APIREST API for Accelo with CRUD access to companies, contacts, activities, tasks, projects (jobs), milestones...26.8 Novo PaymentsNovo money movement - invoicing, ACH transfers, and faster payouts (Express ACH). These capabilities are de...26.3

Emerging 9 Early or largely undocumented

Fawaterak API v2REST API for the EasyPay/Fawaterak payment gateway. Authenticated with a vendor Bearer token, it lists avai...25.4 VAT API v2REST API for EU and UK VAT compliance including VAT rate lookups by country, VAT number validation against ...24.0 QuickBooks Online Accounting APIREST API for managing QuickBooks Online accounting entities including Customer, Vendor, Employee, Item, Inv...22.9 Found InvoicingCreate and send invoices, track their status, and get paid directly into the Found account, with invoice in...22.8 Certinia Billing Central APIGlobal Apex service classes for subscription and usage billing. BillingService, BillingDocumentsService, Bi...22.6 BillDesk CX+ Deep APIDirect REST API access for advanced payment processing, giving merchants full control over checkout UX. Sup...20.8 Carepatron Billing API (Modeled)Modeled product-area API for billing - invoices, payments, and insurance claim management. endpointsModeled...18.0 Heartland Bill Pay APIThe Heartland Bill Pay API enables invoice and bill payment processing for merchants accepting recurring or...14.6 LEAP Time & Billing APIModeled time recording, invoicing, and billing surface, evidenced by LEAP's own marketed "automatic timekee...11.2

Minimal 4 Almost no public developer surface

Knight-Swift EDI IntegrationKnight-Swift Transportation supports EDI integration for freight tendering, shipment tracking, and invoicin...10.6 UBS QR Portal APIA free programmatic QR-bill creation service supporting the Swiss QR payment standard. Returns QR bills in ...10.4 CN eBillCN eBill is the customer tool for managing rail freight invoices, account statements, and online bill payme...10.3 ServicingLease and loan servicing covering invoicing, collections, portfolio management, and asset-level financial t...9.5

Unrated 1 Not yet scored

xCBL — XML Common Business LibraryxCBL 4.0 is a royalty-free library of XML business documents and reusable components for business-to-busine...

Companies reaching this through an API (35)

These companies publish an API, specification or operation carrying “Invoicing” but do not classify their business under it. Listed unranked and kept out of the count above, because one tagged operation is not a statement about what a company does.

Score breakdown

Frequency

65.6

log-scaled weighted occurrences

Breadth

4.8

spread across providers

Quality lift

40.8

mean composite of providers using it

Cohesion

19.4

strength of nearest seed neighbor

Where this tag comes from

Provider tag174

Api tag69

Openapi tag4

Openapi op tag34

Cohort brief

Auto-generated

The 171 providers in the APIs.io catalog tagged Invoicing, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers

171

all scored

Mean Kin Score

36.1

+12.2 vs catalog 23.9

Mean Agent Readiness

+10 vs catalog 12

Spread

3.1–75.7

median 36.3 · σ 15.1

How the 171 split by band

Exemplar 2Strong 25Developing 37Thin 64Emerging 36Minimal 7

Facet averages, against the whole catalog

Facet	This cohort	Catalog	Difference	Scored
Contract Quality	36.8	19.8	+17	171
Developer Ergonomics	37	23.4	+13.6	171
Access Clarity	39.6	26.5	+13.1	171
Operational Transparency	24.7	13.9	+10.8	171
Discoverability	67.8	61.2	+6.6	171
Contract Governance	7.5	6.4	+1.1	171

A facet is averaged over the members that carry it, not over the whole cohort — the “Scored” column is that count. Averaging an absent facet as zero would score our own coverage gaps as the providers’ posture.

What this cohort publishes

Artifact	This cohort	Catalog	Difference
MCP server (any)	20%	10%	+10
MCP server (first-party)	24%	13%	+11
Agent Skills	0%	0%	0
OAuth scopes	26%	11%	+15
Security	99%	96%	+3
Arazzo workflows	2%	2%	0
Governance rules	12%	14%	-2

mcp_pct counts any mcp/ artifact including ones API Evangelist derived from the provider OpenAPI; mcp_first_party_pct counts only servers the provider publishes. Prefer the latter.

Top by Kin Score

1 Square 75.7
2 Stax 75.3
3 Lili 64.5
4 Intuit 62.7
5 Pennylane 62.6
6 Visma 61.9
7 FieldPulse 61.4
8 Resolve 60.6
9 Agave 60.5
10 Slash 60.1

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Tools for tags

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cohort_statsPRO — the distribution across this tag: mean, median, band split, adoption rates.
cohort_rankingsPRO — the leaderboard, on composite AND agent-readiness axes.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

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The distribution (Pro)

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Invoicing

Providers using this tag (173)

APIs with this tag (68)