fix: read ERC-20 token details on chains without multicall3

typescript/.changeset/erc20-token-details-without-multicall3.md

@@ -0,0 +1,5 @@
+---
+"@coinbase/agentkit": patch
+---
+
+Fixed ERC-20 actions (`get_balance`, `transfer`, `approve`, `get_allowance`) failing with "Could not fetch token details" on chains whose viem definition has no `multicall3` address, such as a local Anvil (`foundry`) or custom chains. Token details are now read with plain contract calls when multicall is not available.

typescript/agentkit/src/action-providers/erc20/erc20ActionProvider.test.ts

@@ -1,6 +1,8 @@
 import { erc20ActionProvider } from "./erc20ActionProvider";
 import { TransferSchema, GetTokenAddressSchema, ApproveSchema, AllowanceSchema } from "./schemas";
 import { EvmWalletProvider } from "../../wallet-providers";
+import { ChainDoesNotSupportContract } from "viem";
+import { foundry } from "viem/chains";
 
 const MOCK_AMOUNT = 15;
 const MOCK_DECIMALS = 6;
@@ -34,12 +36,15 @@ describe("Transfer Schema", () => {
 describe("Get Balance Action", () => {
   let mockWallet: jest.Mocked<EvmWalletProvider>;
   let mockMulticall: jest.Mock;
+  let mockReadContract: jest.Mock;
   const actionProvider = erc20ActionProvider();
 
   beforeEach(async () => {
     mockMulticall = jest.fn();
+    mockReadContract = jest.fn();
     const mockPublicClient = {
       multicall: mockMulticall,
+      readContract: mockReadContract,
       getCode: jest.fn().mockResolvedValue("0x"),
     };
 
@@ -80,6 +85,54 @@ describe("Get Balance Action", () => {
     const response = await actionProvider.getBalance(mockWallet, args);
 
     expect(mockMulticall).toHaveBeenCalled();
+    expect(mockReadContract).not.toHaveBeenCalled();
+
+    expect(response).toContain("Error: Could not fetch token details");
+  });
+
+  it("should read the token with plain calls on a chain without multicall3", async () => {
+    mockMulticall.mockRejectedValue(
+      new ChainDoesNotSupportContract({ chain: foundry, contract: { name: "multicall3" } }),
+    );
+    mockReadContract.mockImplementation(async ({ functionName }) => {
+      switch (functionName) {
+        case "name":
+          return "MockToken";
+        case "decimals":
+          return MOCK_DECIMALS;
+        case "balanceOf":
+          return BigInt(MOCK_AMOUNT * 10 ** MOCK_DECIMALS);
+      }
+    });
+
+    const args = {
+      tokenAddress: MOCK_CONTRACT_ADDRESS,
+      address: null,
+    };
+
+    const response = await actionProvider.getBalance(mockWallet, args);
+
+    expect(mockReadContract).toHaveBeenCalledTimes(3);
+    expect(mockReadContract).toHaveBeenCalledWith(
+      expect.objectContaining({ functionName: "balanceOf", args: [MOCK_ADDRESS] }),
+    );
+    expect(response).toContain(
+      `Balance of MockToken (${MOCK_CONTRACT_ADDRESS}) at address ${MOCK_ADDRESS} is ${MOCK_AMOUNT}`,
+    );
+  });
+
+  it("should fail when a plain call fails on a chain without multicall3", async () => {
+    mockMulticall.mockRejectedValue(
+      new ChainDoesNotSupportContract({ chain: foundry, contract: { name: "multicall3" } }),
+    );
+    mockReadContract.mockRejectedValue(new Error("execution reverted"));
+
+    const args = {
+      tokenAddress: MOCK_CONTRACT_ADDRESS,
+      address: null,
+    };
+
+    const response = await actionProvider.getBalance(mockWallet, args);
 
     expect(response).toContain("Error: Could not fetch token details");
   });

typescript/agentkit/src/action-providers/erc20/utils.ts

@@ -26,32 +26,48 @@ export async function getTokenDetails(
   address?: string,
 ): Promise<TokenDetails | null> {
   try {
-    const results = await walletProvider.getPublicClient().multicall({
-      contracts: [
-        {
-          address: contractAddress as Hex,
-          abi: erc20Abi,
-          functionName: "name",
-          args: [],
-        },
-        {
-          address: contractAddress as Hex,
-          abi: erc20Abi,
-          functionName: "decimals",
-          args: [],
-        },
-        {
-          address: contractAddress as Hex,
-          abi: erc20Abi,
-          functionName: "balanceOf",
-          args: [(address || walletProvider.getAddress()) as Hex],
-        },
-      ],
-    });
+    const publicClient = walletProvider.getPublicClient();
+    const contracts = [
+      {
+        address: contractAddress as Hex,
+        abi: erc20Abi,
+        functionName: "name",
+        args: [],
+      },
+      {
+        address: contractAddress as Hex,
+        abi: erc20Abi,
+        functionName: "decimals",
+        args: [],
+      },
+      {
+        address: contractAddress as Hex,
+        abi: erc20Abi,
+        functionName: "balanceOf",
+        args: [(address || walletProvider.getAddress()) as Hex],
+      },
+    ] as const;
 
-    const rawName = results[0].result;
-    const decimals = results[1]?.result;
-    const balance = results[2]?.result;
+    let rawName: string | undefined;
+    let decimals: number | undefined;
+    let balance: bigint | undefined;
+    try {
+      const results = await publicClient.multicall({ contracts });
+      rawName = results[0].result;
+      decimals = results[1]?.result;
+      balance = results[2]?.result;
+    } catch (error) {
+      // Chains whose definition has no Multicall3 address (e.g. local Anvil or custom chains)
+      // cannot use multicall, so read each value with a plain call instead.
+      if ((error as Error)?.name !== "ChainDoesNotSupportContract") {
+        throw error;
+      }
+      [rawName, decimals, balance] = await Promise.all([
+        publicClient.readContract(contracts[0]),
+        publicClient.readContract(contracts[1]),
+        publicClient.readContract(contracts[2]),
+      ]);
+    }
 
     if (balance === undefined || decimals === undefined || rawName === undefined) {
       return null;