MCP Ethers Wallet

Implementation Reference

• src/tools/core.ts:684-727 (handler)

  The handler function implements eth_sign by signing hex-encoded data using the loaded wallet's signMessage method with ethers.getBytes. It checks for wallet availability, converts non-hex data to hex, signs it, and returns the signature and signer address.

  try {
    // First check if a wallet exists
    const wallet = await ethersService.getWallet(provider);
    if (!wallet) {
      return {
        isError: true,
        content: [{ 
          type: "text", 
          text: "No wallet available to sign data. Please create or load a wallet first."
        }]
      };
    }
    
    // Ensure data is in hex format
    let hexData = data;
    if (!data.startsWith("0x")) {
      // Convert string to hex
      hexData = "0x" + Buffer.from(data).toString("hex");
    }
    
    // Sign the data using eth_sign
    // Note: ethers.js v6 doesn't have a direct eth_sign method, so we're using signMessage as an alternative
    // In a real implementation, you'd use a provider's send method with eth_sign
    const signature = await wallet.signMessage(ethers.getBytes(hexData));
    
    return {
      content: [{ 
        type: "text", 
        text: JSON.stringify({
          data: hexData,
          signature,
          signer: wallet.address
        }, null, 2)
      }]
    };
  } catch (error) {
    return {
      isError: true,
      content: [{ 
        type: "text", 
        text: `Error using eth_sign: ${error instanceof Error ? error.message : String(error)}`
      }]
    };
  }

• src/tools/core.ts:678-682 (schema)

  Input schema using Zod: 'data' (string to sign, auto-converted to hex) and optional 'provider' (network reference).

    data: z.string().describe(
      "The data to sign. Will be converted to hex if not already in hex format."
    ),
    provider: z.string().optional().describe(PROVIDER_DESCRIPTION)
  },

• src/tools/core.ts:676-728 (registration)

  Registration of the 'ethSign' tool on the MCP server using server.tool(), providing name, input schema, and handler function.

  "ethSign",
  {
    data: z.string().describe(
      "The data to sign. Will be converted to hex if not already in hex format."
    ),
    provider: z.string().optional().describe(PROVIDER_DESCRIPTION)
  },
  async ({ data, provider }) => {
    try {
      // First check if a wallet exists
      const wallet = await ethersService.getWallet(provider);
      if (!wallet) {
        return {
          isError: true,
          content: [{ 
            type: "text", 
            text: "No wallet available to sign data. Please create or load a wallet first."
          }]
        };
      }
      
      // Ensure data is in hex format
      let hexData = data;
      if (!data.startsWith("0x")) {
        // Convert string to hex
        hexData = "0x" + Buffer.from(data).toString("hex");
      }
      
      // Sign the data using eth_sign
      // Note: ethers.js v6 doesn't have a direct eth_sign method, so we're using signMessage as an alternative
      // In a real implementation, you'd use a provider's send method with eth_sign
      const signature = await wallet.signMessage(ethers.getBytes(hexData));
      
      return {
        content: [{ 
          type: "text", 
          text: JSON.stringify({
            data: hexData,
            signature,
            signer: wallet.address
          }, null, 2)
        }]
      };
    } catch (error) {
      return {
        isError: true,
        content: [{ 
          type: "text", 
          text: `Error using eth_sign: ${error instanceof Error ? error.message : String(error)}`
        }]
      };
    }
  }