SweKit API docs

Conventions

Validators return {"valid": bool, "errors": [codes]} plus parsed fields. HTTP 200 even if the number is invalid; HTTP 400 only for missing/malformed parameters.
Errors: {"error":{"code","message"}}. Rate limit: HTTP 429 with Retry-After.
Response header X-Plan: free | pro | gateway.
POST example: curl -X POST https://swekit-api.zenith-ops.workers.dev/v1/personnummer -H 'content-type: application/json' -d '{"value":"811218-9876"}'

Access & limits

Anonymous demo: 20 requests/min/IP. Higher limits: send X-API-Key: <license key> (600 req/min). Marketplace subscribers use the marketplace's own key and quota. Pro key: contact the operator; pricing is not published.

curl examples

curl "https://swekit-api.zenith-ops.workers.dev/v1/personnummer?value=811218-9876"
curl -X POST "https://swekit-api.zenith-ops.workers.dev/v1/personnummer" -H 'content-type: application/json' -d '{"value":"811218-9876"}'
curl -H 'X-API-Key: YOUR_KEY' "https://swekit-api.zenith-ops.workers.dev/v1/account?clearing=7507&account=1211203"
# error response (missing parameter)
curl "https://swekit-api.zenith-ops.workers.dev/v1/orgnr"

{"error":{"code":"missing_parameter","message":"Missing parameter: value"}}

Error codes

HTTP	Code	Meaning
400	missing_parameter	Required input was not supplied
400	bad_base	OCR base is invalid
400	bad_year	Year must be 1900–2200
400	bad_date	Date must be YYYY-MM-DD
400	bad_input	Business-day input is invalid or out of range
400	invalid_json	POST body is not valid JSON
401	invalid_api_key	API key is invalid or expired
429	rate_limited	Per-minute quota exceeded
500	internal_error	Unexpected server error

MCP client configuration

Claude Desktop (claude_desktop_config.json):

{"mcpServers":{"swekit":{"command":"npx","args":["mcp-remote","https://swekit-api.zenith-ops.workers.dev/mcp"]}}}

Cursor:

{"mcpServers":{"swekit":{"url":"https://swekit-api.zenith-ops.workers.dev/mcp"}}}

VS Code (.vscode/mcp.json):

{"servers":{"swekit":{"type":"http","url":"https://swekit-api.zenith-ops.workers.dev/mcp"}}}

MCP server

Remote MCP endpoint https://swekit-api.zenith-ops.workers.dev/mcp (POST JSON-RPC 2.0: initialize, tools/list, tools/call). Tools: validate_personnummer, validate_orgnr, validate_bankgiro, validate_plusgiro, validate_ocr, generate_ocr, swedish_account_to_iban, validate_iban, lookup_clearing_number, swedish_holidays, swedish_date_info, add_business_days, count_business_days.

Semantics worth knowing

Bank accounts: checksum rules per Bankgirot (type 1 variants 1-2 mod-11; type 2 variants 1/3 mod-10, 2/4 mod-11). Swedbank 8xxx accounts are mod-10 "as a rule" and require the 5th clearing digit for IBAN. Plusgiro cannot be converted to IBAN. Some old accounts do not pass checksums.
Business days (bank mode): Saturdays, Sundays, public holidays plus midsommarafton, julafton and nyårsafton are not business days (these are equated with Sundays for payment deadlines under Swedish law). Use mode=work for plain weekday-minus-red-day logic. Check your own contracts for company-specific rules.
Personnummer: age and century are inferred from the separator (+ = 100+). Gender is from the 9th digit (registered legal sex). Use for validation, not identification.

FAQ

Does a valid number prove an account or person exists?: No. The API checks syntax, dates and checksums only; it is not an identity, ownership or account-existence service.
Are requests stored?: No request data is stored by the service. Use POST for personal numbers so they do not appear in URLs or access logs.
Can I convert Plusgiro to IBAN?: No. Swedish bank accounts can be converted when their clearing range is known; Plusgiro is not a bank account format.
What are the limits?: Anonymous access is 20 requests/minute/IP. A valid Pro key allows 600 requests/minute/key. Pro key: contact the operator; pricing is not published.

Endpoints

`GET /v1/personnummer`

Validate & parse a Swedish personnummer / samordningsnummer

value string Personnummer in any common format (YYMMDD-NNNC, YYYYMMDDNNNC, with + for 100+). Prefer POST JSON {"value": "..."} so the number never appears in a URL.

curl "https://swekit-api.zenith-ops.workers.dev/v1/personnummer?value=811218-9876&at=2026-10-16"

`GET /v1/orgnr`

Validate organisationsnummer, derive legal form and Swedish VAT number (SE#########01)

value string Org no. like 556036-0793, 5560360793, SE556036079301

curl "https://swekit-api.zenith-ops.workers.dev/v1/orgnr?value=556036-0793"

`GET /v1/bankgiro`

Validate bankgiro number (Luhn) and format it

value string 7-8 digits, with or without dash

curl "https://swekit-api.zenith-ops.workers.dev/v1/bankgiro?value=5402-9681"

`GET /v1/plusgiro`

Validate plusgiro number

value string 2-8 digits

curl "https://swekit-api.zenith-ops.workers.dev/v1/plusgiro?value=4-8"

`GET /v1/ocr/validate`

Validate an OCR / payment reference (Luhn check digit, optional length digit)

value string OCR digits

curl "https://swekit-api.zenith-ops.workers.dev/v1/ocr/validate?value=12351"

`GET /v1/ocr/generate`

Generate an OCR reference from a base number

`base`	string	Digits, e.g. invoice number
`length_digit`	boolean	Add length digit (default false)

curl "https://swekit-api.zenith-ops.workers.dev/v1/ocr/generate?base=123&length_digit=true"

`GET /v1/account`

Validate a Swedish bank account (clearing + account, per Bankgirot rules) and convert to IBAN

`number`	string	Full account digits (clearing first), OR
`clearing`	string	Clearing number (4 digits; 5 for Swedbank 8xxx)
`account`	string	Account number without clearing

curl "https://swekit-api.zenith-ops.workers.dev/v1/account?clearing=7507&account=1211203"

`GET /v1/iban`

Validate any IBAN (ISO 13616 mod-97, country length) and identify Swedish banks

value string IBAN, spaces allowed

curl "https://swekit-api.zenith-ops.workers.dev/v1/iban?value=SE45 5000 0000 0583 9825 7466"

`GET /v1/bic`

Validate BIC/SWIFT format

value string 8 or 11 characters

curl "https://swekit-api.zenith-ops.workers.dev/v1/bic?value=ESSESESS"

`GET /v1/clearing`

Look up bank, BIC, IBAN id and account type for a clearing number

value string First 4 digits of the account number

curl "https://swekit-api.zenith-ops.workers.dev/v1/clearing?value=8327"

`GET /v1/holidays`

Swedish public holidays and eves for a year

year integer 1900-2200 (default: current year)

curl "https://swekit-api.zenith-ops.workers.dev/v1/holidays?year=2026"

`GET /v1/date`

Info about a date: weekday (sv/en), ISO week, holiday names, business-day status

`date`	string	YYYY-MM-DD
`mode`	string	"bank" (default; midsommarafton, julafton, nyårsafton also excluded) or "work"

curl "https://swekit-api.zenith-ops.workers.dev/v1/date?date=2026-12-24"

`GET /v1/business-days/add`

Add (or subtract) N business days to a date

`date`	string	YYYY-MM-DD
`days`	integer	Positive or negative, \|n\| <= 3650
`mode`	string	bank (default) or work

curl "https://swekit-api.zenith-ops.workers.dev/v1/business-days/add?date=2026-12-22&days=2"

`GET /v1/business-days/between`

Count business days between two dates

`from`	string	YYYY-MM-DD
`to`	string	YYYY-MM-DD
`mode`	string	bank (default) or work

curl "https://swekit-api.zenith-ops.workers.dev/v1/business-days/between?from=2026-10-16&to=2026-11-16"

Data sources

Bankgirot, Bankernas kontonummer, 2024-02-22.
Bankinfrastruktur i Sverige AB, IBAN and Swedish national account number page (clearing table, data date 2026-10-16).
Holidays: computed (Meeus/Jones/Butcher Easter algorithm + statutory rules).