[unit.co docs via api-evangelist/unit-co]: the Unit API is built on the JSON:API specification with media type application/vnd.api+json, secured with Bearer or JWT tokens, and the sandbox base URL is https://api.s.unit.sh. Point sandbox credentials at the sandbox host: calling production with a sandbox key, or the reverse, fails auth with no useful message. A single REST API covers Applications (onboarding), Customers, deposit accounts, cards, and payments, so one error-handling shape covers every resource.

Context: Two integration basics that break first-time Unit integrations: the error envelope shape and the sandbox host.

## Matched source
Source: Source: https://github.com/api-evangelist/unit-co
Original query: "Unit API: JSON:API error format and sandbox base URL"
Key terms: base, error, format, json, sandbox, unit