write-contract

Instructions

Implementation Reference

• src/tools/write-contract.ts:23-58 (handler)

  The execute handler for the 'write-contract' tool. Simulates the transaction with simulateContract, executes it with writeContract, returns the tx hash or formatted error.

  execute: async (args) => {
    try {
      const { request } = await simulateContract(wagmiConfig, args);
      const result = await writeContract(wagmiConfig, request);
      return {
        content: [
          {
            type: "text",
            text: JSONStringify({
              hash: result,
            }),
          },
        ],
      };
    }
    catch (error) {
      if (error instanceof TransactionExecutionError) {
        return {
          content: [
            {
              type: "text",
              text: error.cause.message,
            },
          ],
        };
      }
      return {
        content: [
          {
            type: "text",
            text: (error as Error).message,
          },
        ],
      };
    }
  },

• src/tools/write-contract.ts:13-22 (schema)

  Input schema using Zod for validating parameters like ABI, address, functionName, args, and gas options.

  parameters: z.object({
    abi: Abi.describe("The contract's ABI."),
    address: Address.describe("The contract's address."),
    functionName: z.string().describe("Function to call on the contract."),
    args: z.unknown().array().optional().describe("Arguments to pass when calling the contract."),
    value: z.coerce.bigint().optional().describe("Value in wei sent with this transaction."),
    maxFeePerGas: z.coerce.bigint().optional().describe("Total fee per gas in wei, inclusive of maxPriorityFeePerGas."),
    maxPriorityFeePerGas: z.coerce.bigint().optional().describe("Max priority fee per gas in wei."),
    chainId: z.coerce.number().optional().describe("Chain ID to validate against before sending transaction."),
  }),

• src/tools/write-contract.ts:9-60 (registration)

  The primary registration function that defines and adds the 'write-contract' tool to the MCP server using server.addTool, including name, description, schema, and handler.

  export function registerWriteContractTools(server: FastMCP, wagmiConfig: Config): void {
    server.addTool({
      name: "write-contract",
      description: "Execute a write function on a contract.",
      parameters: z.object({
        abi: Abi.describe("The contract's ABI."),
        address: Address.describe("The contract's address."),
        functionName: z.string().describe("Function to call on the contract."),
        args: z.unknown().array().optional().describe("Arguments to pass when calling the contract."),
        value: z.coerce.bigint().optional().describe("Value in wei sent with this transaction."),
        maxFeePerGas: z.coerce.bigint().optional().describe("Total fee per gas in wei, inclusive of maxPriorityFeePerGas."),
        maxPriorityFeePerGas: z.coerce.bigint().optional().describe("Max priority fee per gas in wei."),
        chainId: z.coerce.number().optional().describe("Chain ID to validate against before sending transaction."),
      }),
      execute: async (args) => {
        try {
          const { request } = await simulateContract(wagmiConfig, args);
          const result = await writeContract(wagmiConfig, request);
          return {
            content: [
              {
                type: "text",
                text: JSONStringify({
                  hash: result,
                }),
              },
            ],
          };
        }
        catch (error) {
          if (error instanceof TransactionExecutionError) {
            return {
              content: [
                {
                  type: "text",
                  text: error.cause.message,
                },
              ],
            };
          }
          return {
            content: [
              {
                type: "text",
                text: (error as Error).message,
              },
            ],
          };
        }
      },
    });
  };

• src/tools/register-tools.ts:58-58 (registration)

  Top-level registration invocation within the overall registerTools function.

  registerWriteContractTools(server, wagmiConfig);