PaySimple API
PaySimple documents a self-serve REST payments API with a sandbox, HMAC-signed webhooks, and a .NET SDK. Two generations (API 4 and API 5) coexist with different feature sets, so full integrations touch both. Auth is a long-lived plaintext API key; there is no OAuth.
Frequently asked questions
PaySimple scores A on Supergood's API Report Card. PaySimple documents a self-serve REST payments API with a sandbox, HMAC-signed webhooks, and a .NET SDK. Two generations (API 4 and API 5) coexist with different feature sets, so full integrations touch both. Auth is a long-lived plaintext API key; there is no OAuth.
PaySimple has a workable official integration path. Most engineering teams can build against it directly. Open API: self-serve, documented, with SDKs
PaySimple is a cloud-based payment acceptance and recurring-billing platform built for service-based small businesses.
Vertical SMB payments, with explicit go-to-market focus on three EverCommerce-aligned segments: Home & Field Services (contractors, HVAC, plumbers, home improvement, maintenance technicians); Healthcare (physician practices, behavioral health, urgent care, with HIPAA-compliant configuration); and Fitness & Wellness (gyms, yoga/pilates studios, salons, spas, med spas, massage therapists, personal trainers). A service business owner signs up for PaySimple (often pushed by their EverCommerce vertical SaaS, e.g., a HVAC contractor on ServiceFusion, a therapist on DrChrono, a salon on SalonBiz), runs a credit check / merchant underwriting, and gets a merchant account with PaySimple as the processor.
Mid-tier within US SMB service-business payments. Latka reports approximately 17,000 paying customers and ~$8M direct ARR for PaySimple itself; EverCommerce reports ~20,000 service professionals on PaySimple and 745,000+ customers across the broader portfolio.
PaySimple holds the AR nervous system for the ~17k-20k SMB service businesses that run on it.
Mature and actively maintained but visibly two-generation. PaySimple launched in 2005 and was acquired by EverCommerce in 2017.
Two coexisting API generations (API 4 legacy + API 5 beta) with non-overlapping feature sets, integrators are explicitly told 'you may need to access both' to ship a complete integration. Authentication uses a long-lived API key passed as plaintext (not Base64) in a `basic` header tied to the merchant account, no OAuth, no scopes, no per-integration key rotation. Full sourced list under Sources below.
Common alternatives include Stripe, Square, PayPal / Braintree, Authorize.net (Visa), Helcim, GoCardless. Graded alternatives appear under "More from the report card" below.
Supergood's grades measure one thing: can a customer's engineering team get their own data out programmatically? Supergood checks six things (whether a real API exists, how access is gated, data coverage, auth quality, docs and developer experience, and stability) and rolls them into a letter grade. Supergood re-verifies grades, and they only move on evidence.
Not that we could find. As of August 2026 there is no official PaySimple MCP server in any public registry, and no maintained community server we're aware of. We re-verify this periodically — report an inaccuracy below if we missed one.
Not natively. PaySimple doesn't publish an MCP server, so MCP clients like Claude, Cursor, and Codex have nothing to connect to out of the box. If that changes, this page will reflect it.