Public APIs For Monthly CPI (Consumer Price Index) For All Countries?

Hi everyone,

I’m building a small CLI tool and I’m looking for public (or at least well-documented) APIs that provide monthly CPI / inflation data for as many countries as possible.

Requirements / details:

• Coverage: ideally global (all or most countries)
• Frequency: monthly (not just annual)
• Data type:
  • CPI index level (e.g. 2015 = 100), not only inflation % YoY
  • Headline CPI is fine; bonus if core CPI is also available
• Access:
  • Public or free tier available
  • REST / JSON preferred
• Nice to have:
  • Country codes mapping (ISO / IMF / WB)
  • Reasonable uptime / stability
  • Historical depth (10–20+ years if possible)

One use case of the CLI tool is to select a country, specify a past year, type a nominal value of budget at that year and contact by API an online provider to retrieve the mentioned information above and compute the real value of that budget at the current time.

Are there reliable data providers or APIs (public or freemium) that expose monthly CPI data globally?

Thanks!