arbdebug_validationInputsAt

Retrieve validation inputs for specific messages on Arbitrum networks to debug and verify transaction processing using debug APIs.

Instructions

Get validation inputs at a specific message (requires debug API)

Input Schema

TableJSON Schema

Name	Required	Description
`rpcUrl`	No	The RPC URL of the Arbitrum node (optional if default is set)
`chainName`	No	Chain name (e.g., 'Xai', 'Arbitrum One') - will auto-resolve to RPC URL
`msgNum`	Yes	Message number to get validation inputs for
`target`	No	Target for validation inputs

Implementation Reference

src/index.ts:633-650 (handler)

MCP tool handler for 'arbdebug_validationInputsAt': resolves RPC URL from args or chainName, instantiates NitroNodeClient, calls getValidationInputsAt(msgNum, target), returns JSON-formatted result.

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

src/index.ts:1435-1462 (registration)

Tool registration in getAvailableTools(): defines name, description, and inputSchema (rpcUrl optional, chainName optional, msgNum required, target optional). Returned by ListTools handler.

  name: "arbdebug_validationInputsAt",
  description:
    "Get validation inputs at a specific message (requires debug 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",
      },
      msgNum: {
        type: "number",
        description: "Message number to get validation inputs for",
      },
      target: {
        type: "string",
        description: "Target for validation inputs",
      },
    },
    required: ["msgNum"],
  },
},

src/index.ts:1439-1461 (schema)

Input schema definition for the tool: object with optional rpcUrl/chainName, required msgNum (number), optional target (string).

  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",
    },
    msgNum: {
      type: "number",
      description: "Message number to get validation inputs for",
    },
    target: {
      type: "string",
      description: "Target for validation inputs",
    },
  },
  required: ["msgNum"],
},

src/clients/nitro-node-client.ts:385-407 (helper)

Helper method in NitroNodeClient: converts msgNum to hex, optionally adds target, calls RPC 'arbdebug_validationInputsAt', returns inputs or error.

async getValidationInputsAt(
  msgNum: number,
  target?: string
): Promise<ValidationInputs> {
  try {
    const params = [`0x${msgNum.toString(16)}`];
    if (target) {
      params.push(target);
    }

    const inputs = await this.makeRpcCall(
      "arbdebug_validationInputsAt",
      params
    );
    return { inputs };
  } catch (error) {
    return {
      inputs: null,
      error: `Validation inputs not supported on this RPC endpoint: ${
        (error as Error).message
      }`,
    };
  }

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