Arbitrum MCP Server

Instructions

Implementation Reference

• src/index.ts:579-595 (handler)

  MCP tool handler for 'arbtrace_block': resolves RPC URL using chain name or provided URL, creates NitroNodeClient instance, calls traceBlock method, and returns JSON-formatted result.

  case "arbtrace_block": {
    const rpcUrl = await this.resolveRpcUrl(
      (args.rpcUrl as string) || (args.chainName as string)
    );
    const nodeClient = new NitroNodeClient(rpcUrl);
    const result = await nodeClient.traceBlock(
      args.blockNumOrHash as string
    );
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(result, null, 2),
        },
      ],
    };
  }

• src/index.ts:1352-1376 (schema)

  Input schema definition for the 'arbtrace_block' tool, specifying parameters like rpcUrl, chainName (optional), and required blockNumOrHash, along with description.

  {
    name: "arbtrace_block",
    description:
      "Get trace information for all transactions in a block (requires trace API)",
    inputSchema: {
      type: "object" as const,
      properties: {
        rpcUrl: {
          type: "string",
          description:
            "The RPC URL of the Arbitrum node (optional if default is set)",
        },
        chainName: {
          type: "string",
          description:
            "Chain name (e.g., 'Xai', 'Arbitrum One') - will auto-resolve to RPC URL",
        },
        blockNumOrHash: {
          type: "string",
          description: "Block number or hash to trace",
        },
      },
      required: ["blockNumOrHash"],
    },
  },

• src/index.ts:93-102 (registration)

  Registration of ListToolsRequestSchema handler that returns the list of available tools, including 'arbtrace_block' via getAvailableTools().

  this.server.setRequestHandler(ListToolsRequestSchema, async () => {
    try {
      console.error("Handling list tools request");
      return {
        tools: this.getAvailableTools(),
      };
    } catch (error) {
      console.error("Error in list tools handler:", error);
      throw error;
    }

• src/clients/nitro-node-client.ts:325-337 (helper)

  Helper method traceBlock in NitroNodeClient that performs the actual RPC call to 'arbtrace_block' with blockNumOrHash parameter, handles errors gracefully.

  async traceBlock(blockNumOrHash: string): Promise<TraceResult> {
    try {
      const traces = await this.makeRpcCall("arbtrace_block", [blockNumOrHash]);
      return { traces };
    } catch (error) {
      return {
        traces: null,
        error: `Trace block not supported on this RPC endpoint: ${
          (error as Error).message
        }`,
      };
    }
  }