blocknative-mcp

Instructions

Estimate gas cost for a transaction based on gas limit, confidence level, and chain.

Parameters:
- gas_limit (int): The gas limit for the transaction (e.g., 21000 for a simple transfer).
- confidence (int): The confidence level for gas price prediction (0-100).
- chain_id (int): The ID of the blockchain network (e.g., 1 for Ethereum Mainnet). Default: 1.
- ctx (Optional[Context]): The MCP context object. Default: None.

Implementation Reference

• src/blocknative_mcp/cli.py:99-139 (handler)

  The handler function for the 'estimate_gas_cost' tool, decorated with @mcp.tool() for registration. It validates inputs, fetches gas prices using the helper, selects the closest confidence prediction, calculates the total gas cost in Gwei and ETH, and returns a formatted string.

  @mcp.tool()
  async def estimate_gas_cost(gas_limit: int, confidence: int = 99, chain_id: int = 1, ctx: Optional[Context] = None) -> str:
      """
      Estimate gas cost for a transaction based on gas limit, confidence level, and chain.
  
      Parameters:
      - gas_limit (int): The gas limit for the transaction (e.g., 21000 for a simple transfer).
      - confidence (int): The confidence level for gas price prediction (0-100).
      - chain_id (int): The ID of the blockchain network (e.g., 1 for Ethereum Mainnet). Default: 1.
      - ctx (Optional[Context]): The MCP context object. Default: None.
      """
      if not (0 <= confidence <= 100):
          return "Error: Confidence must be between 0 and 100"
      if gas_limit <= 0:
          return "Error: Gas limit must be positive"
      
      data = await fetch_gas_prices(chain_id)
      if "error" in data:
          return data["error"]
      
      # Find the closest confidence level
      predictions = data["estimatedPrices"]
      closest_prediction = min(
          predictions,
          key=lambda p: abs(p.get("confidence", 0) - confidence),
          default={}
      )
      
      if not closest_prediction:
          return "Error: No matching gas price prediction found"
      
      max_fee = closest_prediction.get("maxFeePerGas", 0)
      total_cost_gwei = max_fee * gas_limit
      total_cost_eth = total_cost_gwei / 1e9  # Convert Gwei to ETH
      
      return (
          f"Estimated Gas Cost (Confidence {confidence}%, Chain ID {chain_id}):\n"
          f"- Gas Limit: {gas_limit}\n"
          f"- Max Fee Per Gas: {max_fee} Gwei\n"
          f"- Total Cost: {total_cost_gwei} Gwei ({total_cost_eth:.6f} ETH)"
      )

• src/blocknative_mcp/cli.py:19-48 (helper)

  Supporting helper function that fetches gas price data from the Blocknative API, extracts predictions and base fee, and handles errors. Used by the estimate_gas_cost handler.

  async def fetch_gas_prices(chain_id: int = 1) -> Dict:
      """Fetch gas price predictions from Blocknative API for a given chain."""
      try:
          headers = {"Authorization": BLOCKNATIVE_API_KEY} if BLOCKNATIVE_API_KEY else {}
          async with httpx.AsyncClient() as client:
              response = await client.get(
                  BLOCKNATIVE_GAS_API_URL,
                  headers=headers,
                  params={"chainid": chain_id}
              )
              response.raise_for_status()
              data = response.json()
          
          # Extract relevant fields from the response
          block_prices = data.get("blockPrices", [])
          if not block_prices:
              return {"error": "No block prices found in API response"}
          
          # Use the first block's data
          first_block = block_prices[0]
          return {
              "baseFeePerGas": first_block.get("baseFeePerGas", 0),
              "estimatedPrices": first_block.get("estimatedPrices", []),
              "unit": data.get("unit", "gwei"),
              "system": data.get("system", "unknown"),
              "network": data.get("network", "unknown")
          }
      except httpx.HTTPError as e:
          return {"error": f"Failed to fetch gas prices for chain ID {chain_id}: {str(e)}"}

• src/blocknative_mcp/cli.py:100-109 (schema)

  Function signature with type annotations and docstring defining the input parameters and return type, serving as the tool schema.

  async def estimate_gas_cost(gas_limit: int, confidence: int = 99, chain_id: int = 1, ctx: Optional[Context] = None) -> str:
      """
      Estimate gas cost for a transaction based on gas limit, confidence level, and chain.
  
      Parameters:
      - gas_limit (int): The gas limit for the transaction (e.g., 21000 for a simple transfer).
      - confidence (int): The confidence level for gas price prediction (0-100).
      - chain_id (int): The ID of the blockchain network (e.g., 1 for Ethereum Mainnet). Default: 1.
      - ctx (Optional[Context]): The MCP context object. Default: None.
      """

• src/blocknative_mcp/cli.py:99-99 (registration)

  The @mcp.tool() decorator registers the estimate_gas_cost function as an MCP tool.

  @mcp.tool()