API/Sign-in

Exchange a one-time code for an API key

POST/v1/sign-ins/{sign_in_id}/confirmation· no key needed

Confirms a sign-in with the code from the email and returns a new key. The secret appears in this response and nowhere else, ever.

The first confirmation for an address creates the account on the Free plan.
Every later confirmation adds a key to that account, and the address is sent a notice that a key was created.

A wrong code is 422, with the attempts left on the problem. Once a sign-in has been used, has expired or has run out of attempts, it answers 410 and a new one has to be requested. An unknown sign_in_id is also 410, never 404, so the endpoint cannot be used to probe which ids exist.

Request

curl -X POST https://api.einvoicing.dev/v1/sign-ins/<sign_in_id>/confirmation \  -H "Content-Type: application/json" \  -d '{ "code": "482913", "key": { "name": "CLI on steve-laptop", "mode": "live" } }'

<?php$client = new GuzzleHttp\Client();$response = $client->request('POST', 'https://api.einvoicing.dev/v1/sign-ins/<sign_in_id>/confirmation', [    'headers' => [        'Accept' => 'application/json',    ],    'json' => [        'code' => '482913',        'key' => [            'name' => 'CLI on steve-laptop',            'mode' => 'live',        ],    ],]);$data = json_decode((string) $response->getBody(), true)['data'];

payload := `{  "code": "482913",  "key": {    "name": "CLI on steve-laptop",    "mode": "live"  }}`req, _ := http.NewRequest(http.MethodPost, "https://api.einvoicing.dev/v1/sign-ins/<sign_in_id>/confirmation", strings.NewReader(payload))req.Header.Set("Content-Type", "application/json")res, err := http.DefaultClient.Do(req)if err != nil {	log.Fatal(err)}defer res.Body.Close()

const res = await fetch("https://api.einvoicing.dev/v1/sign-ins/<sign_in_id>/confirmation", {  method: "POST",  headers: {    "Content-Type": "application/json",  },  body: JSON.stringify({    "code": "482913",    "key": {      "name": "CLI on steve-laptop",      "mode": "live"    }  }),});const { data } = await res.json();

Parameters

Name	In	Type	Description
`sign_in_id`required	path	Ulid	The `id` returned by `POST /v1/sign-ins`.

Request body

application/json· required

Field	Type	Description
`code`required	string	The six-digit code from the email.
`key`	KeyRequest	How to set up a new key.

Example bodyapplication/json

{  "code": "482913",  "key": {    "name": "CLI on steve-laptop",    "mode": "live"  }}

Response

201

The code was accepted and a key was created. Store key.secret now.

Field	Type	Description
`data`required	SignInResult	The account signed in to, and the key the sign-in created.

Example responseapplication/json

{  "data": {    "account": {      "id": "01J9Z3M8W2C4K6P8R0T2V4X6Z8",      "email": "[email protected]",      "plan": "free",      "created_at": "2026-09-11T14:05:02.117Z"    },    "account_created": true,    "key": {      "id": "01J9Z3M8X5D7F9H1K3M5P7R9T1",      "name": "CLI on steve-laptop",      "mode": "live",      "prefix": "einv_live_k3m9x2qa",      "created_at": "2026-09-11T14:05:02.117Z",      "last_used_at": null,      "expires_at": null,      "revoked_at": null,      "secret": "einv_live_k3m9x2qa_Zx81QmPq4sVt7LwN2cBy6RfJ0hKd9GuTe3Ao5W"    }  }}

Errors

Every error is application/problem+json (RFC 9457). Branch on type, which is stable, never on title or detail.

Status	When
400	The body could not be parsed as the XML or JSON its `Content-Type` declares. Distinct from `422`, which means the body parsed and its contents were rejected. Problem `type` is `malformed-body`. /problems/malformed-body
410	This sign-in can no longer be used. It was already used, expired, ran out of attempts, or never existed. Request a new one with `POST /v1/sign-ins`. Problem `type` is `sign-in-expired`. /problems/sign-in-expired
422	The code was wrong (`invalid-code`, with `attempts_remaining`), or the body did not match this schema (`invalid-request`).
429	Too many requests in a short window. Slow down and retry after the number of seconds in `Retry-After`. Problem `type` is `rate-limited`. /problems/rate-limited

Schemas

ConfirmSignInRequest

The emailed code, and optionally how to set up the key it produces.

Field	Type	Description
`code`required	string	The six-digit code from the email.
`key`	KeyRequest	How to set up a new key.

KeyRequest

How to set up a new key.

Field	Type	Description
`name`required	string	What the key is for, so it can be recognised later. It is not secret.
`mode`	string	`live` keys are metered and can manage the account; `test` keys are free and cannot. `livetest`
`expires_at`	string or null · date-time	When the key stops working. Null means it never expires. Short expiries suit CI.

SignInResult

The account signed in to, and the key the sign-in created.

Field	Type	Description
`account`required	Account	An account. Identified by its email address; it has no password.
`account_created`required	boolean	True when this sign-in created the account.
`key`required	NewApiKey	A key as created, the only time its secret is ever shown. The fields of `ApiKey` plus `secret`. It is spelled out in full rather than composed with `allOf`, because `ApiKey` refuses unknown fields and would reject `secret`.