Validate ISBN & Book Listing Data API

What it does

Validate ISBN & Book Listing Data helps you check and prepare the identifiers and listing text for a book before it goes on sale. Send an ISBN, a book record, a description or a listing title, and get back a structured result you can use in your own forms, imports and publishing tools.

Use the ISBN endpoint to check whether an ISBN-10 or ISBN-13 is valid. It converts between the two forms and returns the hyphenated versions, the registration group and the barcode digits. Use the ONIX endpoint to turn one book record into an ONIX 3.0 product message, the metadata format distributors and retailers use. It returns the XML and a list of warnings and errors, so you can see what is missing before you send it.

Use the description endpoint to clean a book blurb into the limited HTML that retailers accept. It tells you which tags were removed or converted and whether the text fits the length limit. Use the listing endpoint to check an online shop listing title and tags against the marketplace's rules: title length, repeated symbols, banned characters, tag count and tag length. It returns plain-language findings you can show to a seller before they save.

It fits catalog imports, publishing tools, listing editors and any backend that needs consistent book identifiers and listing data.

▣ ENDPOINT 01 / 04

POST

ISBN checker and converter

https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/isbn

QUICKSTART

GUIDE

Quickstart

Validate an ISBN by sending it in a simple JSON body.

curl -X POST "https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/isbn" \
  -H "apy-token: $APY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"isbn":"9780306406157"}'

What you'll get back

Returns a JSON object with no declared top-level fields in the output schema.

{
  "result": {
    "input": "9780306406157",
    "clean": "9780306406157",
    "kind": "isbn13",
    "wellFormed": true,
    "valid": true,
    "convertedFromCorrected": false,
    "rangesVersion": "2026-10-30",
    "givenCheck": "7",
    "expectedCheck": "7",
    "isbn10": "0306406152",
    "isbn13": "9780306406157",
    "isbn10Hyphenated": "0-306-40615-2",
    "isbn13Hyphenated": "978-0-306-40615-7",
    "groupName": "English language",
    "rangeStatus": "ok",
    "barcodeDigits": "9780306406157"
  }
}

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API key

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About this endpoint

What it does

Validates an ISBN sent in the request body and returns a success response. The detailed response shape is not yet defined in the output schema.

Request Body

Parameter	Type	Mandatory	Description
isbn	String	Yes	ISBN value to validate. String with 1 to 40 characters.

Response

Returns a JSON object with a single result object describing the ISBN you sent, with its check-digit result and the converted and hyphenated forms.

Field	Type	Description
`result.input`	string	The value you sent, exactly as received.
`result.clean`	string	The input with spaces, hyphens and any `ISBN` prefix removed.
`result.kind`	string	The detected type: `isbn13`, `isbn10` or `unknown`.
`result.wellFormed`	boolean	`true` if the value has the right length and characters for an ISBN.
`result.valid`	boolean	`true` if the check digit is correct.
`result.convertedFromCorrected`	boolean	`true` when the converted forms were built from a corrected check digit.
`result.givenCheck`	string	The check digit in your input.
`result.expectedCheck`	string	The check digit the number should have.
`result.isbn10`	string	The ISBN-10 form, when one exists.
`result.isbn13`	string	The ISBN-13 form.
`result.isbn10Hyphenated`	string	The ISBN-10 with hyphens in the standard places.
`result.isbn13Hyphenated`	string	The ISBN-13 with hyphens in the standard places.
`result.groupName`	string	The registration group, such as `English language`.
`result.rangeStatus`	string	`ok` when the number falls in an assigned range. Otherwise hyphenation isn't possible.
`result.barcodeDigits`	string	The 13 digits to encode in an EAN-13 barcode.
`result.rangesVersion`	string	The date of the ISBN range data used for hyphenation.
`result.error`	string	A plain-language reason, present only when the input isn't a usable ISBN.

▣ ENDPOINT 02 / 04

POST

ONIX generator

https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/onix

QUICKSTART

GUIDE

Quickstart

Validate a book listing by sending the required ONIX fields as JSON.

curl -X POST "https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/onix" \
  -H "apy-token: $APY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "title": "The Pragmatic Programmer",
    "contributors": [
      {
        "name": "Andrew Hunt"
      }
    ],
    "isbn": "9780135957059",
    "publisher": "Addison-Wesley Professional",
    "pubDate": "1999-10-30"
  }'

What you'll get back

Returns a JSON object. The response schema does not declare any top-level fields.

{
  "result": {
    "issues": [
      {
        "field": "pageCount",
        "message": "Print editions usually need a page count.",
        "level": "warning"
      },
      {
        "field": "subjects",
        "message": "No subject code. Most retailers and distributors ask for at least one BISAC or Thema code.",
        "level": "warning"
      },
      {
        "field": "description",
        "message": "No description. Retailers normally show it on the product page.",
        "level": "warning"
      }
    ],
    "xml": "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<ONIXMessage release=\"3.0\" xmlns=\"http://ns.editeur.org/onix/3.0/reference\">\n  <Header>\n    <Sender>\n      <SenderName>Test Press</SenderName>\n    </Sender>\n    <SentDateTime>20261112T072538Z</SentDateTime>\n  </Header>\n  <Product>\n    <RecordReference>9780306406157</RecordReference>\n    <NotificationType>03</NotificationType>\n    <ProductIdentifier>\n      <ProductIDType>15</ProductIDType>\n      <IDValue>9780306406157</IDValue>\n    </ProductIdentifier>\n    <ProductIdentifier>\n      <ProductIDType>03</ProductIDType>\n      <IDValue>9780306406157</IDValue>\n    </ProductIdentifier>\n    <DescriptiveDetail>\n      <ProductComposition>00</ProductComposition>\n      <ProductForm>BC</ProductForm>\n      <TitleDetail>\n        <TitleType>01</TitleType>\n        <TitleElement>\n          <TitleElementLevel>01</TitleElementLevel>\n          <TitleText>Test Book</TitleText>\n        </TitleElement>\n      </TitleDetail>\n      <Contributor>\n        <SequenceNumber>1</SequenceNumber>\n        <ContributorRole>A01</ContributorRole>\n        <PersonName>Jane Doe</PersonName>\n      </Contributor>\n      <Language>\n        <LanguageRole>01</LanguageRole>\n        <LanguageCode>eng</LanguageCode>\n      </Language>\n    </DescriptiveDetail>\n    <PublishingDetail>\n      <Publisher>\n        <PublishingRole>01</PublishingRole>\n        <PublisherName>Test Press</PublisherName>\n      </Publisher>\n      <PublishingStatus>04</PublishingStatus>\n      <PublishingDate>\n        <PublishingDateRole>01</PublishingDateRole>\n        <Date dateformat=\"00\">20260115</Date>\n      </PublishingDate>\n    </PublishingDetail>\n    <ProductSupply>\n      <Market>\n        <Territory>\n          <RegionsIncluded>WORLD</RegionsIncluded>\n        </Territory>\n      </Market>\n      <SupplyDetail>\n        <Supplier>\n          <SupplierRole>01</SupplierRole>\n          <SupplierName>Test Press</SupplierName>\n        </Supplier>\n        <ProductAvailability>20</ProductAvailability>\n        <Price>\n          <PriceType>01</PriceType>\n          <PriceAmount>9.99</PriceAmount>\n          <CurrencyCode>USD</CurrencyCode>\n        </Price>\n      </SupplyDetail>\n    </ProductSupply>\n  </Product>\n</ONIXMessage>\n"
  }
}

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API key

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About this endpoint

What it does

Generates ONIX book-listing data from the submitted book metadata. The request body must include the required book fields, and the endpoint returns a success acknowledgement with no response fields defined in the schema.

Request Body

Parameter	Type	Mandatory	Description
isbn	String	Yes	ISBN for the book.
title	String	Yes	Book title.
prices	Object Array	No	List of price objects. Each item includes `amount` and `currency`; `type` is optional.
prices[].type	String	No	Price type.
prices[].amount	String	Yes	Price amount.
prices[].currency	String	Yes	Price currency.
pubDate	String	Yes	Publication date. Format: `YYYYMMDD`, `YYYY-MM-DD`, or `YYYY-MM`.
audience	String	No	Audience value.
language	String	No	Language code or value.
subjects	Object Array	No	List of subject objects. Each item includes `scheme` and `code`. `scheme` is limited to `bisac` or `thema`.
subjects[].code	String	Yes	Subject code.
subjects[].scheme	ENUM	Yes	Subject scheme. Allowed values: `bisac`, `thema`.
subtitle	String	No	Subtitle.
pageCount	String	No	Page count.
publisher	String	Yes	Publisher name.
territory	String	No	Territory value.
description	String	No	Long description.
productForm	String	No	ONIX form code, for example `BC` paperback or `BB` hardback.
availability	String	No	Availability value.
contributors	Object Array	Yes	List of contributor objects. Each item includes `name`; `role` is optional and defaults to `A01` (author).
contributors[].name	String	Yes	Contributor name.
contributors[].role	String	No	ONIX role code, default `A01` (author).
contributors[].inverted	String	No	Inverted contributor name.
shortDescription	String	No	Short description.

Response

Returns a JSON object with a single result object containing the ONIX 3.0 message and a list of issues found in the book record.

Field	Type	Description
`result.xml`	string	The ONIX 3.0 product message as XML. Present when the record has no error-level issues.
`result.issues[]`	array	Problems found in the record. Empty when the record is complete.
`result.issues[].field`	string	The request field the issue is about, such as `pageCount` or `subjects`.
`result.issues[].message`	string	A plain-language description of what to fix or review.
`result.issues[].level`	string	`error` blocks the XML. `warning` flags missing or questionable data and the XML is still returned.

▣ ENDPOINT 03 / 04

POST

Book description HTML formatter

https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/kdp-description

QUICKSTART

GUIDE

Quickstart

Send your HTML or plain text book description for KDP-friendly cleanup.

curl -X POST "https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/kdp-description" \
  -H "apy-token: $APY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"html": "<h1>Big</h1><p>A gripping <b>debut</b> novel.</p><script>alert(1)</script>"}'

What you'll get back

Returns a JSON object.

{
  "result": {
    "html": "<h4>Big</h4><p>A gripping <b>debut</b> novel.</p>",
    "removed": {
      "script": 1
    },
    "changed": {
      "h1": 1
    },
    "stats": {
      "htmlLength": 49,
      "visible": 26,
      "words": 5,
      "overBy": 0
    },
    "notes": []
  }
}

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API key

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About this endpoint

What it does

Formats book description content for KDP by taking an input body with either HTML or plain text and returning a cleaned result. The request body supports html, text, and an optional heading level, but the output schema is not yet defined beyond a JSON object wrapper.

Request Body

Parameter	Type	Mandatory	Description
html	String	No	HTML to clean to the tags KDP allows. Maximum length: 200000 characters.
text	String	No	Plain text; blank lines make paragraphs. Maximum length: 200000 characters.
heading	ENUM	No	Allowed values: `h4`, `h5`, `h6`.

Response

Returns a JSON object with a single result object containing the cleaned, KDP-ready HTML, a record of what was changed, and length statistics.

Field	Type	Description
`result.html`	string	The description as HTML that Amazon KDP accepts.
`result.removed`	object	Tags that were stripped, as tag name to count, for example `{"script": 1}`. Empty when nothing was removed.
`result.changed`	object	Tags that were converted to an allowed tag, as tag name to count, for example `{"h1": 1}`. Empty when nothing was changed.
`result.stats.htmlLength`	number	Length of the returned `html`, in characters.
`result.stats.visible`	number	Number of characters of text readers will see, without the tags.
`result.stats.words`	number	Word count of the visible text.
`result.stats.overBy`	number	How many characters the description is over KDP's limit. `0` means it fits.
`result.notes[]`	array of strings	Plain-language issues worth fixing, for example when nothing is bold or a heading. Empty when there are none.

▣ ENDPOINT 04 / 04

POST

Etsy listing checker

https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/etsy-listing-check

QUICKSTART

GUIDE

Quickstart

Check whether an Etsy listing title and optional tags are valid for an ISBN book listing.

curl -X POST "https://api.eu.apyhub.com/freedailypro/validate-isbn-book-listing-data/etsy-listing-check" \
  -H "apy-token: $APY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"title": "Salt & Pepper & Spice Set", "tags": "kitchen, spice rack, gift"}'

What you'll get back

Returns a JSON object. The output schema doesn’t declare any top-level fields, so the response shape is intentionally unspecified here.

{
  "result": {
    "title": {
      "length": 25,
      "front": "Salt & Pepper & Spice Set",
      "findings": [
        {
          "severity": "ok",
          "text": "25 of 140 characters used."
        },
        {
          "severity": "error",
          "text": "The title uses \"&\" 2 times. Etsy allows each of % : & only once in a title."
        },
        {
          "severity": "advice",
          "text": "A very short title leaves search phrases unused. Add what it is, who it is for and one or two details such as material or size."
        }
      ],
      "errors": 1
    },
    "tags": {
      "tags": [
        {
          "tag": "kitchen",
          "length": 7,
          "problems": [],
          "inTitle": false
        },
        {
          "tag": "spice rack",
          "length": 10,
          "problems": [],
          "inTitle": false
        },
        {
          "tag": "gift",
          "length": 4,
          "problems": [],
          "inTitle": false
        }
      ],
      "findings": [
        {
          "severity": "advice",
          "text": "3 of 13 tags used. Each unused tag is a search phrase left on the table."
        }
      ],
      "errors": 0,
      "titleWordsNotInTags": [
        "salt",
        "pepper",
        "set"
      ],
      "cleaned": [
        "kitchen",
        "spice rack",
        "gift"
      ]
    }
  }
}

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API key

Loading your default key…

The full key is used to call the gateway and stays in this tab — never sent to orbit or saved.

About this endpoint

What it does

Checks Etsy listing data by sending a listing title and optional tags to the endpoint. The response schema is not yet defined, so the exact success payload shape is not documented here.

Request Body

Parameter	Type	Mandatory	Description
title	String	Yes	Listing title. Maximum length: 1000 characters.
tags	String	No	Tags separated by commas or new lines. Maximum length: 5000 characters.

Response

Returns a JSON object with a single result object holding the title check and the tags check.

Field	Type	Description
`result.title.length`	number	Length of the title in characters. Etsy allows up to 140.
`result.title.front`	string	The first 40 characters of the title, the part buyers see first in search results.
`result.title.findings[]`	array	Findings about the title.
`result.title.findings[].severity`	string	`ok`, `advice` or `error`. `error` means Etsy's rules are broken.
`result.title.findings[].text`	string	A plain-language description of the finding.
`result.title.errors`	number	Number of `error` findings in the title.
`result.tags.tags[]`	array	One entry per tag, in the order sent, after removing duplicates.
`result.tags.tags[].tag`	string	The tag text.
`result.tags.tags[].length`	number	Length of the tag in characters. Etsy allows up to 20.
`result.tags.tags[].problems[]`	array of strings	Problems with this tag, such as being too long. Empty when the tag is fine.
`result.tags.tags[].inTitle`	boolean	`true` if the tag's words already appear in the title.
`result.tags.findings[]`	array	Findings about the tag list as a whole, with the same `severity` and `text` fields as the title findings.
`result.tags.errors`	number	Number of `error` findings in the tags.
`result.tags.titleWordsNotInTags[]`	array of strings	Words in the title that no tag covers yet.
`result.tags.cleaned[]`	array of strings	The tag list with duplicates removed.

▣ COMMON ERRORS

Errors any endpoint can return

400bad_request

Required parameter missing or malformed body.

401unauthorized

API key missing, revoked, or not authorized for this service.

429rate_limited

Your plan's per-second rate exceeded. Retry with exponential backoff.

503upstream_busy

Backend temporarily unavailable. Try again in a few seconds.

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