™2 min read
typeThe class
codeThe reason
paramThe field
Parse all four fields
Never act on the HTTP status alone.
const { type, code, message, param } = (await res.json()).error;
log.warn({ status: res.status, code, param, message });Decide from type + code
Use type for the retry/no-retry split and code for the specific behaviour, per the envelope reference. Look up an unfamiliar code in the catalogue.
Surface the right thing
Show users a message derived from code (never the raw message, which may change), and point form errors at the field named in param.
Frequently asked questions
Why not just show error.message to users?
The message is for developers and may be reworded over time. Map the stable code to your own user-facing copy.
What if param is absent?
Then the error is not about one specific field (e.g. a rate limit or a server error). Only field-validation errors carry param.
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