Meta Generator

The Salvium Meta Generator is a web application that builds correctly structured, hex-encoded metadata for Salvium token creation. It removes the need to hand-craft JSON and compute hashes manually.

Live tool: meta-generator.salvium.io (or run locally — see below)

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What it produces

For every token you configure, the Meta Generator outputs:

Output	Used for
Pretty JSON	Human-readable preview and documentation
Compact JSON	The exact string that gets hashed and encoded
Hex payload	The token_metadata_hex value passed to create_token
SHA-256 hash	The hash value passed to create_token
Byte size	The size value passed to create_token

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Supported token standards

Select your standard from the form and the relevant fields appear automatically:

Standard	Fields shown
ERC-721 / ERC-1155	Image URI, animation URL, external URL, attributes
ERC-3643 / ERC-1400	RWA fields — asset type, jurisdiction, valuation, documents
CIP-108 / OpenZeppelin-Governor	Governance fields — proposal text, voting period, quorum
Any	Optional compliance section — MiCAR class, LEI, whitepaper

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Using the tool

1. Fill in the required fields

• Name — the human-readable token name (also written to Tier 1 on-chain)
• Asset ID — a unique identifier: ISIN, legal reference, invoice number, or proposal number

2. Choose a standard

Select the standard that matches your token type. This controls which extension fields appear. See Token Types for guidance.

3. Fill in extension fields

For RWA tokens, enter the valuation, jurisdiction, and any document hashes. For NFTs, add the image URI and attributes.

4. Review the JSON preview

The right-hand panel updates in real time. Check that the output looks correct before exporting.

5. Export

• Copy hex — copies the token_metadata_hex value ready to paste into a create_token call
• Copy hash — copies the SHA-256 hash
• Download .hex — saves the hex payload to a file for CLI workflows

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Technical details

The Meta Generator performs these steps in the browser:

1. Builds the Tier 2 JSON object from your form inputs
2. Serialises it to compact UTF-8 JSON (no whitespace) — this is the canonical form that gets hashed
3. Encodes the compact JSON to hex (each byte → two hex characters, no 0x prefix)
4. Computes SHA-256 of the compact JSON bytes
5. Reports the byte length (using TextEncoder for accurate UTF-8 byte counting)

Why compact JSON?

The hash and byte size must match exactly between what the Meta Generator reports and what you send to create_token. Any difference in whitespace or key ordering would break the integrity check. Always use the compact form for transport.

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Running locally

git clone https://github.com/salvium/salvium-metadata-generator
cd salvium-metadata-generator
npm install
npm run dev

Opens at http://localhost:5173.

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Integration with create_token

Once you have the three values from the Meta Generator, pass them directly to create_token:

curl http://127.0.0.1:29088/json_rpc \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "id": "0",
    "method": "create_token",
    "params": {
      "ticker": "PROP",
      "supply": 1,
      "name": "123 High Street Property Token",
      "url": "https://your-server.com/metadata/PROP.json",
      "token_metadata_hex": "<hex from Meta Generator>",
      "hash": "<hash from Meta Generator>",
      "size": <size from Meta Generator>
    }
  }'

Or pass the metadata object to the SalviumAssetSDK and it handles encoding automatically.

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Known issues

Issue	Status
token_metadata_hex previously exported with 0x prefix — would fail at RPC	Fixed in current version
CLI command preview previously showed create_asset instead of create_token	Fixed in current version