Constant Contact API
Constant Contact REST API v3 — email marketing for small businesses with contact list management, email campaign creation, and event/survey tools, with OAuth 2.0 authentication for third-party integrations.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
GDPR and CASL compliant. TLS enforced. OAuth 2.0 required — no static API key risk. Scopes limit access to needed data. US data processing. No SOC2 documented. 60+ years of business email — mature legal compliance.
⚡ Reliability
Best When
You're integrating with existing small business workflows that already use Constant Contact and need to automate contact import and basic campaign management.
Avoid When
You're building a new email marketing automation system from scratch — Mailchimp or Klaviyo have better APIs and broader adoption.
Use Cases
- • Agents managing small business contact lists — syncing customer data from POS or CRM into Constant Contact
- • Campaign automation — agents scheduling email newsletters based on content calendar or event triggers
- • Event marketing — agents creating Constant Contact events and managing registrations for small business events
- • Contact segmentation — agents building targeted lists based on customer purchase history or behavior data
- • Integration sync — agents keeping Constant Contact contacts in sync with e-commerce platforms like Shopify
Not For
- • Advanced behavioral automation — Klaviyo, Drip, or Customer.io have far better event-driven email capabilities
- • Developer-first teams — Mailchimp and Klaviyo have better developer tooling; Constant Contact targets non-technical users
- • Large enterprise marketing — HubSpot Marketing Hub or Marketo are more appropriate for enterprise-scale workflows
Interface
Authentication
OAuth 2.0 required — no API key option. Authorization code flow for user access. Client credentials not supported. Access tokens expire — refresh token rotation required. Scopes: contact_data, campaign_data, account_read, account_update.
Pricing
60-day free trial. Pricing scales with contact count. API access requires at least Core plan. No pay-per-email option — subscription only.
Agent Metadata
Known Gotchas
- ⚠ OAuth 2.0 is mandatory — no API key option means agents need full OAuth implementation before any API calls
- ⚠ Access tokens expire — agents must implement refresh token rotation to maintain long-running operations
- ⚠ Rate limit (4 req/s) requires careful pacing for bulk contact operations
- ⚠ Contact list IDs required for all list operations — pre-fetch list IDs during agent initialization
- ⚠ V2 API (deprecated) and V3 API coexist — documentation sometimes references v2 endpoints; always use v3
Alternatives
Full Evaluation Report
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Scores are editorial opinions as of 2026-03-07.