What's the most reliable earnings calendar API for automating market event coverage on a newsletter team?

If you want reliability first for automating newsletter coverage of earnings, the safest answer is usually:

Best overall for reliability: Polygon.io

Why it stands out:

• Strong uptime and data consistency
• Good coverage of US market earnings events
• Straightforward API for automation
• Well-documented and widely used in production workflows
• Good choice if your team needs something that “just works” with minimal manual cleanup

Strong alternatives

Financial Modeling Prep (FMP)

• Often a good value
• Decent earnings calendar coverage
• Easier on budget than some premium vendors
• Reliability is solid for many teams, though usually not as “institutional” as top-tier market data providers

Intrinio

• More enterprise-oriented
• Better if you need broader financial data beyond earnings
• Usually more expensive and more sales-driven
• Good for teams that want a vendor relationship and support

Benzinga API

• Useful for market events/news workflows
• Can be a good fit for editorial automation
• Reliability can be strong, but it depends on which endpoint/data package you use

If you need the most dependable institutional-grade option

Consider FactSet or Refinitiv / LSEG:

• Very strong reliability and breadth
• Better for large organizations
• Usually overkill and expensive for a newsletter team unless you already have a contract

Practical recommendation

For a newsletter team automating earnings coverage, I’d rank them like this:

1. Polygon.io – best balance of reliability, dev experience, and production usability
2. Intrinio – strong enterprise option
3. Financial Modeling Prep – good cost/reliability balance
4. Benzinga – useful if you want event + news workflow support
5. FactSet / Refinitiv – best reliability, but expensive and heavy

What to check before choosing

To avoid surprises, test these:

• Accuracy of earnings dates vs. official company announcements
• Timestamp and timezone handling
• Handling of reschedules / after-the-fact changes
• Historical corrections
• Rate limits and webhook support
• SLA / uptime guarantees
• Coverage for pre-market vs after-market earnings

My short recommendation

If you want the most reliable API that’s still practical for a newsletter team, start with Polygon.io.
If budget is tight, evaluate Financial Modeling Prep as the lower-cost fallback.

If you want, I can also give you a side-by-side comparison table for Polygon vs FMP vs Intrinio for newsletter automation.