Idna bidi check

idna-bidi-check · version 1.0.0 · Numbers & math · free, no key needed

Apply the RFC 5893 Bidi Rule to one label and name the first failing condition.

Use when you need to: check the idna bidi rule · rfc 5893 label direction test · right to left label ending check.

Decide before calling

Read the versioned contract and the supported scope below. Reuse idna-bidi-check@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use idna-bidi-check@1.0.0 for check the idna bidi rule. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• check the idna bidi rule
• rfc 5893 label direction test
• right to left label ending check
• does this label mix arabic and european digits
• bidi condition for a domain label
• when does the bidi rule apply
• בדיקת כיוון אותיות בתווית

Not supported

• reject disallowed code points
• punycode encode the label
• apply one bidi rule to a whole multi-label domain

Behavior

• RFC 5893 only. Disallowed characters, hyphens, NFC, and punycode are not judged.
• enforce when_rtl: if the label has no Bidi_Class R, AL, or AN, applicable is false, valid is true, and direction is none.
• enforce always: the six conditions run even when no RTL class is present. A first class other than L, R, or AL fails bidi_condition_1.
• direction is rtl when the first class is R or AL, ltr when it is L, and none otherwise. RTL then checks conditions 2, 3, and 4. LTR checks 5 then 6. The first failure wins.
• reason_index and cp identify the failing code point. first_rtl_index is the first R, AL, or AN, or null.
• Results are not a homograph, phishing, DNS, or authenticity verdict. No DNS query is performed.

Input

• label (string, required): min length 1; max length 252
• enforce (one of "when_rtl", "always", required)

Output

• valid (boolean, required)
• applicable (boolean, required)
• direction (one of "ltr", "rtl", "none", required)
• reason (one of null, "bidi_condition_1", "bidi_condition_2", "bidi_condition_3", "bidi_condition_4", "bidi_condition_5", "bidi_condition_6", required)
• reason_index (integer or null, required): min 0; max 251
• cp (integer or null, required): min 0; max 1114111
• first_rtl_index (integer or null, required): min 0; max 251
• data_version (constant "idna2008-rfc5892-unicode-15.1.0", required)

Limits

• max label bytes: 252
• max output bytes: 8192

Example

Request input:

{
  "label": "a",
  "enforce": "when_rtl"
}

Response:

{
  "result": {
    "valid": true,
    "applicable": false,
    "direction": "none",
    "reason": null,
    "reason_index": null,
    "cp": null,
    "first_rtl_index": null,
    "data_version": "idna2008-rfc5892-unicode-15.1.0"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "idna-bidi-check",
  "version": "1.0.0",
  "input": {
    "label": "a",
    "enforce": "when_rtl"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/idna-bidi-check/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"label":"a","enforce":"when_rtl"}'

The machine-readable contract is at /v1/tools/idna-bidi-check/versions/1.0.0.

CLI

node cli.mjs run idna-bidi-check 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

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