# day3

**Canonical:** https://apis.io/providers/day3-app/  
**Website:** https://day3.app/  
**APIs profiled:** 2

Day3 provides email marketing and transactional email services billed by the number of emails sent. It offers unlimited subscribers, tiered pricing starting at $1 per month, and features such as deliverability tools, GDPR compliance, and one‑click unsubscribe. The platform targets startups and indie developers looking for a simple, usage‑based pricing model.

## Kin Score — 51.8 / 100 (developing)

Scored 2026-11-06 under rubric 0.27.0.

| Facet | Score |
|---|---|
| Discoverability | 48.2 |
| Contract Quality | 33.8 |
| Contract Governance | 22.0 |
| Operational Transparency | 34.2 |
| Developer Ergonomics | 50.0 |
| Access Clarity | 92.1 |

Regulatory layer — **Horizontal (data, software, accessibility, platform)**: 35.3 (matched via fallback).

## Agent readiness — 44.2 (agent-ready)

| Dimension | Value |
|---|---|
| Spec Presence | yes |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | no |
| Auth Clarity | served |
| Idempotency | verified |
| Error Semantics | no |
| OpenAPI Examples | partial |
| Rate Limit Signal | no |
| Event Surface Described | yes |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |
| Delegated Identity | served |
| Protected Resource Metadata | verified |
| Dynamic Client Registration | yes |
| Agentic Commerce | no |
| Pagination Ratio | partial |
| Operation Distinctiveness | no |
| MCP Tool Quality | na |

## Access

Paid — onboarding: unknown, pricing: paid, trial: no (confidence: medium).

## APIs (2)

- **Day3 API** — Public API for Day3 email marketing and transactional email services. Documentation is available at the developer portal.
- **day3 API** — day3 API as documented publicly: 19 operations. Contract generated from the documentation by API Evangelist (2026-11-05); not the provider's own document.

## Security (4)

- **Day3 App Authentication** — 1 scheme
- **Day3 App Domain Security** — TLSv1.3 · HSTS · DMARC
- **Day3 App Vulnerability Disclosure** — security.txt · contact published
- **Day3 App Trust Center** — SOC 2, GDPR

## Plans (1)

- **Day3 App Plans Pricing**

## Tags

Email Marketing, Transactional Email, Software-as-a-Service, Startup Tools

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/day3-app/). Scores are computed from the provider's own public artifacts under a published rubric.