cardano-protocol-params

# cardano-protocol-params ## When to use - Fetching fresh protocol parameters - Understanding fee calculation inputs - Debugging min-UTxO or execution budget issues - Comparing params across networks ## Operating rules (must follow) - Always fetch fresh params for the target network - Never assume mainnet params apply to testnets - Keep pparams.json with tx artifacts for reproducibility ## Key parameters explained ### Fee calculation ``` minFeeA: 44 # lovelace per byte minFeeB: 155381 # base fee in lovelace ``` Formula: `fee = minFeeA * txSize + minFeeB` ### Min UTxO ``` coinsPerUTxOByte: 4310 # lovelace per byte of UTxO ``` Minimum ADA required = size of UTxO (including datum) × coinsPerUTxOByte ### Execution units (Plutus) ``` maxTxExecutionUnits: steps: 10000000000 # CPU budget memory: 10000000 # Memory budget executionUnitPrices: priceSteps: 0.0000721 # lovelace per step priceMemory: 0.0577 # lovelace per memory unit ``` ### Reference scripts ``` minFeeRefScriptCostPerByte: 15 # Cost for using reference scripts ``` ## Workflow ### Fetch parameters ```bash # Preprod cardano-cli conway query protocol-parameters \ --testnet-magic 1 \ --out-file pparams-preprod.json # Mainnet cardano-cli conway query protocol-parameters \ --mainnet \ --out-file pparams-mainnet.json ``` ### Extract key values ```bash # Using jq cat pparams.json | jq '{ minFeeA: .txFeePerByte, minFeeB: .txFeeFixed, coinsPerUTxOByte: .utxoCostPerByte, maxTxSize: .maxTxSize, maxValSize: .maxValueSize }' ``` ### Calculate min-UTxO for output ```bash # Approximate: base ~160 bytes + datum size # For simple ADA-only output: ~1 ADA minimum # For output with tokens: varies by token count/names ``` ## Examples ### Example: Debug "UTxO too small" error **Problem:** Transaction fails with min-UTxO error **Response:** ```bash # 1. Fetch current params cardano-cli conway query protocol-parameters \ --testnet-magic 1 \ --out-file pparams.json # 2. Check coinsPerUTxOByte cat pparams.json | jq .utxoCostPerByte # Result: 4310 # 3. Estimate min-UTxO for your output # Simple ADA output: ~160 bytes × 4310 = ~690,000 lovelace # With inline datum: add datum size × 4310 # With tokens: add ~30 bytes per token # 4. Solution: increase output amount above minimum ``` ### Example: Estimate script execution cost **Problem:** Need to budget for Plutus script **Response:** ```bash # 1. Get execution prices cat pparams.json | jq '{ priceSteps: .executionUnitPrices.priceSteps, priceMemory: .executionUnitPrices.priceMemory }' # 2. If script uses 1M steps and 100K memory: # Cost = (1000000 × 0.0000721) + (100000 × 0.0577) # Cost = 72.1 + 5770 = 5842.1 lovelace (~0.006 ADA) # 3. Add to base tx fee for total ``` ## Network magic reference ``` Mainnet: (no flag, use --mainnet) Preprod: --testnet-magic 1 Preview: --testnet-magic 2 ``` ## Safety / key handling - Protocol params are public, no secrets involved - Always verify you're querying the intended network - Store pparams with tx artifacts for debugging ## References - `shared/PRINCIPLES.md` - [Cardano Protocol Parameters](https://docs.cardano.org)