Fungible Token#

Instruction text for agents that use the Fungible Token skill, loaded by bb dev skills fungible-token and the MCP get_skill_instructions tool.

Try it#

Paste this into Claude Code, Codex, or Cursor with the BitBadges MCP server wired. The agent loads the skill, builds, verifies, and hands back a link to review and sign.

Load the fungible-token skill and build me one: simple fungible token with fixed or unlimited supply and configurable mint/transfer approvals. Use the session tools, run validate, review, and simulate in parallel, fix anything critical, then call get_review_url and give me the link.

From a shell, bb dev skills fungible-token prints the same instructions.

Summary#

Required standards: ["Fungible Tokens"]

• validTokenIds: must be exactly [{ "start": "1", "end": "1" }] (single token ID)
• All tokens share the same token ID (1), making them interchangeable
• Amount field in transfers determines quantity
• Token metadata must reference token ID 1
• Ownership times typically forever: [{ "start": "1", "end": "18446744073709551615" }]

Instructions#

Fungible Token Configuration#

When creating a fungible token collection, you must follow these requirements:

Required Configuration#

1. validTokenIds: Set to exactly [{ "start": "1", "end": "1" }]

   • This ensures only token ID 1 is valid
   • This is the standard pattern for fungible tokens

2. Standards: Include "Fungible Tokens" in the standards array

   • Example: "standards": ["Fungible Tokens"]

3. Token Metadata: Each tokenMetadata entry must reference token ID 1

   • Example: "tokenIds": [{ "start": "1", "end": "1" }]

Supply Tracking with approvalAmounts#

Fungible tokens use approvalAmounts (not predeterminedBalances) to track minting supply:

{
  "approvalCriteria": {
    "overridesFromOutgoingApprovals": true,
    "approvalAmounts": {
      "overallApprovalAmount": "1000000",
      "perInitiatedByAddressApprovalAmount": "1000",
      "perToAddressApprovalAmount": "0",
      "perFromAddressApprovalAmount": "0",
      "amountTrackerId": "mint-tracker",
      "resetTimeIntervals": { "startTime": "0", "intervalLength": "0" }
    }
  }
}

• overallApprovalAmount: total supply cap (use "0" for unlimited)
• perInitiatedByAddressApprovalAmount: max per user (use "0" for unlimited)
• Important: predeterminedBalances and approvalAmounts are incompatible, fungible tokens use approvalAmounts, not predeterminedBalances

Pattern-Specific Gotchas#

• All tokens share the same token ID (1), making them interchangeable
• Amount field in transfers determines quantity (e.g., "amount": "100" means 100 tokens)
• Ownership times are typically forever: [{ "start": "1", "end": "18446744073709551615" }]

Common Mistakes#

• Don't use predeterminedBalances for fungible tokens, use approvalAmounts instead. They are incompatible.
• Don't use numbers instead of strings for amounts, use "1000" not 1000. All numeric values must be string-encoded.
• Don't forget autoApproveAllIncomingTransfers: true in defaultBalances, without it, recipients cannot receive tokens on public-mint collections.
• Don't forget overridesFromOutgoingApprovals: true on Mint approvals, required for all fromListId: "Mint" approvals.
• Don't use multiple token IDs, fungible tokens must use exactly one token ID [{ "start": "1", "end": "1" }].

Example Structure#

{
  "updateValidTokenIds": true,
  "validTokenIds": [{ "start": "1", "end": "1" }],
  "updateStandards": true,
  "standards": ["Fungible Tokens"],
  "updateTokenMetadata": true,
  "tokenMetadata": [{
    "uri": "ipfs://...",
    "customData": "",
    "tokenIds": [{ "start": "1", "end": "1" }]
  }]
}