EVM MCP Server

Instructions

Implementation Reference

• src/core/tools.ts:1106-1145 (handler)

  The handler function that implements the core logic of the 'read_contract' tool. It parses the ABI if necessary, constructs ReadContractParameters, calls the underlying readContract helper, formats the result using helpers.formatJson, and handles errors appropriately.

      abi,
      functionName,
      args = [],
      network = 'ethereum'
    }) => {
      try {
        // Parse ABI if it's a string
        const parsedAbi = typeof abi === 'string' ? JSON.parse(abi) : abi;
  
        const params = {
          address: contractAddress as Address,
          abi: parsedAbi,
          functionName,
          args
        };
  
        const result = await services.readContract(params, network);
  
        return {
          content: [
            {
              type: 'text',
              text: services.helpers.formatJson(result)
            }
          ]
        };
      } catch (error) {
        return {
          content: [
            {
              type: 'text',
              text: `Error reading contract: ${error instanceof Error ? error.message : String(error)}`
            }
          ],
          isError: true
        };
      }
    }
  );

• src/core/tools.ts:1079-1105 (schema)

  Zod schema defining the input parameters for the 'read_contract' tool, including contractAddress, abi (JSON array), functionName, optional args array, and optional network.

      .string()
      .describe('The address of the smart contract to interact with'),
    abi: z
      .array(z.any())
      .describe(
        'The ABI (Application Binary Interface) of the smart contract function, as a JSON array'
      ),
    functionName: z
      .string()
      .describe(
        "The name of the function to call on the contract (e.g., 'balanceOf')"
      ),
    args: z
      .array(z.any())
      .optional()
      .describe(
        "The arguments to pass to the function, as an array (e.g., ['0x1234...'])"
      ),
    network: z
      .string()
      .optional()
      .describe(
        "Network name (e.g., 'ethereum', 'optimism', 'arbitrum', 'base', 'polygon') or chain ID. Defaults to Ethereum mainnet."
      )
  },
  async ({
    contractAddress,

• src/core/tools.ts:1076-1146 (registration)

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

    "Read data from a smart contract by calling a view/pure function. This doesn't modify blockchain state and doesn't require gas or signing.",
    {
      contractAddress: z
        .string()
        .describe('The address of the smart contract to interact with'),
      abi: z
        .array(z.any())
        .describe(
          'The ABI (Application Binary Interface) of the smart contract function, as a JSON array'
        ),
      functionName: z
        .string()
        .describe(
          "The name of the function to call on the contract (e.g., 'balanceOf')"
        ),
      args: z
        .array(z.any())
        .optional()
        .describe(
          "The arguments to pass to the function, as an array (e.g., ['0x1234...'])"
        ),
      network: z
        .string()
        .optional()
        .describe(
          "Network name (e.g., 'ethereum', 'optimism', 'arbitrum', 'base', 'polygon') or chain ID. Defaults to Ethereum mainnet."
        )
    },
    async ({
      contractAddress,
      abi,
      functionName,
      args = [],
      network = 'ethereum'
    }) => {
      try {
        // Parse ABI if it's a string
        const parsedAbi = typeof abi === 'string' ? JSON.parse(abi) : abi;
  
        const params = {
          address: contractAddress as Address,
          abi: parsedAbi,
          functionName,
          args
        };
  
        const result = await services.readContract(params, network);
  
        return {
          content: [
            {
              type: 'text',
              text: services.helpers.formatJson(result)
            }
          ]
        };
      } catch (error) {
        return {
          content: [
            {
              type: 'text',
              text: `Error reading contract: ${error instanceof Error ? error.message : String(error)}`
            }
          ],
          isError: true
        };
      }
    }
  );
  
  // Write to contract

• src/core/services/contracts.ts:270-276 (helper)

  Helper function re-exported from services that performs the actual contract read using viem's publicClient.readContract. Called by the tool handler.

  export async function readContract(
    params: ReadContractParameters,
    network = 'ethereum'
  ) {
    const client = getPublicClient(network);
    return await client.readContract(params);
  }