# MainStreet

**Canonical:** https://apis.io/providers/mainstreet/  
**Website:** https://mainstreet.ai/  
**APIs profiled:** 1

MainStreet is a US small-business tax-credit and back-office platform that identifies, calculates, and files R&D tax credits alongside a client's CPA. Its service covers qualified research expense (QRE) identification under IRC §41, the IRS four-part test, business-component documentation, Form 6765 preparation (including the mandatory Section G component-level reporting that begins with tax years starting after 31 December 2025), the §41(h) payroll-tax offset for pre-revenue startups, and state R&D credits across 30+ states. Beyond R&D it claims SECURE Act retirement-plan credits, the Small Business Health Care Tax Credit, and the Disabled Access Credit, and it sells adjacent back-office services — entity formation, banking, expense tracking, and bookkeeping and tax filing. MainStreet was founded in 2019 as a venture-backed R&D tax-credit fintech and was acquired by Employer.com in May 2025; the brand now operates as part of that back-office suite. MainStreet ships no public product API, developer portal, or OpenAPI definition — it is an API consumer (payroll data via Finch, document generation via Anvil) rather than an API producer. Its only public machine-readable contract is the OpenID Connect and RFC 8414 discovery pair served by its identity host.

## Kin Score — 30.6 / 100 (thin)

Scored 2026-08-19 under rubric 0.12.0. Trend: flat (+0.3 from 30.3).

| Facet | Score |
|---|---|
| Discoverability | 87.0 |
| Contract Quality | 0.0 |
| Governance | 18.2 |
| Contract Governance | 18.2 |
| Operational Transparency | 15.8 |
| Developer Ergonomics | 50.0 |
| Commercial Clarity | 38.2 |
| Access Clarity | 38.2 |

## Agent readiness — 8.5 (agent-aware)

| Dimension | Value |
|---|---|
| Spec Presence | no |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | no |
| Auth Clarity | yes |
| Idempotency | no |
| Error Semantics | no |
| OpenAPI Examples | no |
| Rate Limit Signal | no |
| Event Surface Described | no |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## APIs (1)

- **MainStreet Identity (OpenID Connect)** — The OpenID Connect / OAuth 2.0 authorization surface behind MainStreet sign-in, served from login.mainstreet.com on an Auth0 tenant. It publishes a complete OIDC Discovery 1.0 d...

## Security (2)

- **Mainstreet Authentication** — openIdConnect/oauth2 · 1 scheme
- **Mainstreet Domain Security** — TLSv1.3 · HSTS · DMARC

## Tags

Company, Tax, Tax Credits, Accounting, Financial Services, Small Business, Fintech, Bookkeeping, Compliance, Payroll

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/mainstreet/). Scores are computed from the provider's own public artifacts under a published rubric.