Mundi Czarter / developers

Mundi Czarter API

Public, read-only REST API: free sailing yachts and prices for a date range on the Masurian Lakes (Poland). Version 1. No API key, no sign-up.

Quickstart

Which yachts are free from 30 April to 4 May 2027 for at least 6 people, and at what price?

curl -s "https://mundiczarter.pl/api/v1/availability?from=2027-04-30&to=2027-05-04&bunks=6"

Response (shortened):

{
  "ok": true,
  "generatedAt": "2026-10-22T18:13:19Z",
  "currency": "PLN",
  "query": { "arrival": "2027-04-30", "departure": "2027-05-04", "nights": 4, "minBerths": 6, "type": null },
  "count": 13,
  "yachts": [
    {
      "name": "Antila 26cc - Anquilla",
      "url": "https://mundiczarter.pl/yacht/czarter-antila-26cc-anquilla-mazury",
      "berths": 8, "cabins": 3, "lengthM": 7.8, "depositPLN": 2000,
      "arrival": "2027-04-30", "departure": "2027-05-04", "nights": 4,
      "totalPricePLN": 2014, "originalPricePLN": 2120, "discountPercent": 5,
      "pricePerNightPLN": 503.5, "shortenedStay": false,
      "bookingUrl": "https://mundiczarter.pl/yacht/czarter-antila-26cc-anquilla-mazury?from=2027-04-30&to=2027-05-03"
    }
  ],
  "notes": ["..."]
}

The API never makes a reservation. Book through bookingUrl or by phone: +48 534 122 305.

Authentication, API keys and sandbox

There are no API keys and no accounts: every endpoint is public and read-only, so the production API is safe to test against and no separate sandbox is needed. Fair use is enforced by rate limiting (below).

Endpoint

GET /api/v1/availability (HEAD also supported). /api/availability is an unversioned alias of the current major version; use /api/v1/ for stability.

Parameter	Required	Description
`from`	yes	Arrival date (first night), `YYYY-MM-DD`. Not in the past, at most 548 days ahead.
`to`	yes	Departure date (the day the yacht is returned), `YYYY-MM-DD`; 1 to 30 nights after `from`.
`bunks`	no	Minimum number of berths, 1-20.
`type`	no	Yacht model, e.g. `Antila 27`, `Antila 26cc`, `Antila 28.2`, `Antila 30`.

Prices are guest prices in PLN including First Minute / Last Minute discounts, without coupons and optional fees. Season rules apply as on the website: in the main season (June-August) charters run Saturday to Saturday, and package periods such as the May long weekend are rented whole; a request that breaks these rules returns an empty list with an explanation in notes. Where a neighbouring booking leaves only part of the requested range free, the yacht is returned with shortenedStay: true and its own arrival/departure dates.

Errors

Errors are returned as application/problem+json (RFC 9457) with a stable machine-readable code, a human-readable detail and a hint on how to fix the request:

HTTP/1.1 400 Bad Request
Content-Type: application/problem+json

{
  "type": "https://mundiczarter.pl/developers#error-invalid-parameter",
  "title": "Invalid parameter",
  "status": 400,
  "detail": "Data przyjazdu nie moze byc w przeszlosci.",
  "code": "invalid_parameter",
  "hint": "Required: from (arrival) and to (return day) as YYYY-MM-DD, 1-30 nights. Optional: bunks (1-20), type (e.g. \"Antila 27\"). See https://mundiczarter.pl/openapi.json",
  "documentation": "https://mundiczarter.pl/developers"
}

The detail text of validation errors may be in Polish; rely on code and status.

Status	`code`	Meaning and what to do
400	`invalid_parameter`	Missing or invalid parameter. Fix the request according to `hint`.
404	`not_found`	No such endpoint under `/api/`. The only endpoint is `/api/v1/availability`.
405	`method_not_allowed`	Use GET or HEAD (see the `Allow` header).
429	`rate_limited`	Too many requests; wait `Retry-After` seconds. Cache responses: they stay valid for 10 minutes.
500	`internal_error`	Unexpected server error. Retry later; if it persists call +48 534 122 305.

Rate limits and caching

30 requests per 10 minutes per IP address; above that the API answers 429 with Retry-After (seconds).
Every response, including errors and cached answers, carries the quota state so clients can self-throttle:

Header	Meaning
`RateLimit-Limit`	Quota of the window (30).
`RateLimit-Remaining`	Requests left in the window.
`RateLimit-Reset`	Seconds until the window resets.
`RateLimit-Policy`	Structured field, e.g. `"default";q=30;w=600`.
`RateLimit`	Structured field, e.g. `"default";r=29;t=600` (remaining; seconds to reset).
`Retry-After`	On `429` only: seconds to wait.

RateLimit-Limit: 30
RateLimit-Remaining: 29
RateLimit-Reset: 600
RateLimit-Policy: "default";q=30;w=600
RateLimit: "default";r=29;t=600

Responses are cached on the server for up to 10 minutes (X-Cache: HIT|MISS; generatedAt tells when the data was computed). Cached answers do not use up the quota. Final availability is confirmed by the calendar on the yacht page.
CORS is open (Access-Control-Allow-Origin: *); responses carry X-Robots-Tag: noindex.

Versioning and deprecation policy

The version is in the URL path: /api/v1/…. Every response has API-Version: 1.
Breaking changes are released only as a new major version (/api/v2/…). Adding optional parameters or response fields is not breaking and may happen in v1 at any time: clients must ignore unknown fields.
A deprecated version keeps working for at least 12 months after its successor is announced.
Deprecation is signalled with the Deprecation and Sunset response headers (RFC 9745, RFC 8594), in openapi.json and on this page.

Machine-readable descriptions and tools

OpenAPI 3.1 specification with typed error schema (Problem).
API catalog (RFC 9727, application/linkset+json).
llms-full.txt: fleet, prices, discounts and terms for AI assistants; every page also answers Accept: text/markdown.
No official CLI or SDK: a single curl call (see Quickstart) is all that is needed.

Support

Questions or problems: mundij@op.pl, +48 534 122 305, contact page.