Core Concepts
The rules that hold across every endpoint: errors, rate limits, pagination, formats and identifiers.
These pages describe the rules that hold across every endpoint. Read them once and the reference pages stop holding surprises.
| Page | What it covers |
|---|---|
| Errors | The error envelope, the rule for branching on a failure, and the catalogue of code values by status. |
| Rate limits | How many requests you may send, the headers that report your budget, and what a 429 looks like. |
| Pagination | The parameters each list endpoint takes, the pagination object, and how to walk a list to the end. |
| Data formats and IDs | Units and types for money, dates and flags, and which identifier each endpoint expects — yours or Moon's. |
| Metadata | Attaching your own key-value data to a resource, the limits it must fit, and the replace-in-full rule when you change it. |
| Glossary | The vocabulary these docs use, and the API surface each term maps to. |
If you are integrating for the first time, start with Issuing your first card for V1 or the V2 quickstart and come back here when you hit your first 400.
Last updated August 24, 2026