ActiveCampaign vs MoEngage

ActiveCampaign

The v3 REST API covers contacts, segments, campaign scheduling and bulk import, with OpenAPI 3.1 definitions inside public Markdown reference pages and documented Retry-After on 429s. Each user has one unscoped API key, the limit is 5 requests a second, and no changelog was found. The status page shows three critical incidents between 27 July and 28 September 2026.

MoEngage

MoEngage publishes 36 OpenAPI files covering 140 operations, a per-endpoint rate limit table, Markdown docs and a hosted MCP server that builds drafts and leaves publishing to a person. No price, trial or self-serve signup is published, and on 17 August 2026 the Inform API in one data centre accepted requests for about 16 hours without sending the messages.

ActiveCampaign

1. Take the base URL from Settings, Developer in the account. Do not build it from the account name, because non-US accounts may not sit on api-us1.com
2. Use POST /contact/sync to upsert by email, and POST /import/bulk_import for up to 250 contacts, then read each row's outcome from GET /import/info
3. Page large contact sets with orders[id]=ASC and id_greater, not offset. Unsupported filter and order keys are silently ignored
4. Check succeeded in the body after scheduling, pausing or stopping a campaign. Business-rule failures return 200 with succeeded set to 0
5. Stay under 5 requests a second per account and wait for the Retry-After value on a 429

MoEngage

1. Take the data centre number from the dashboard URL and call https://api-{dc}.moengage.com. Data can't be moved between data centres
2. Send an Idempotency-Key header (UUID v4) on V5 campaign writes and test sends, and a transaction_id on Inform alerts, which deduplicates for 5 minutes
3. Use internal event and attribute names in segment filters, and run deep_validate_segment_filters first. A wrong event name is accepted and the count later fails with no reason
4. Use in with a list for text equality in segment filters. equals returns a 400 that names no field
5. Reuse an OAuth access token until it nears expiry. The token endpoint allows 5 requests a minute and 30 per 10 minutes for each key