update_expense

Instructions

Implementation Reference

• src/tools/updateExpense.ts:115-154 (handler)

  Primary handler logic for the update_expense tool. Validates input parameters, extracts update data, calls Brex API via helper function, and returns a formatted JSON response.

  registerToolHandler("update_expense", async (request: ToolCallRequest) => {
    try {
      // Validate parameters
      const params = validateParams(request.params.arguments);
      logDebug(`Updating expense with ID: ${params.expense_id}`);
      
      // Get Brex client
      const brexClient = getBrexClient();
      
      try {
        // Extract the update data (everything except the expense_id)
        const { expense_id, ...updateData } = params;
        
        // Update the expense
        const updateResult = await updateExpense(brexClient, expense_id, updateData);
        
        logDebug(`Successfully updated expense with ID: ${updateResult.id}`);
        
        return {
          content: [{
            type: "text",
            text: JSON.stringify({
              status: "success",
              expense_id: updateResult.id,
              updated_at: updateResult.updated_at,
              expense_status: updateResult.status,
              updated_fields: Object.keys(updateData).filter(key => updateData[key as keyof typeof updateData] !== undefined),
              message: `Expense ${updateResult.id} was updated successfully.`
            }, null, 2)
          }]
        };
      } catch (apiError) {
        logError(`Error updating expense: ${apiError instanceof Error ? apiError.message : String(apiError)}`);
        throw new Error(`Failed to update expense: ${apiError instanceof Error ? apiError.message : String(apiError)}`);
      }
    } catch (error) {
      logError(`Error in update_expense tool: ${error instanceof Error ? error.message : String(error)}`);
      throw error;
    }
  });

• src/tools/updateExpense.ts:54-75 (helper)

  Core helper function that executes the Brex API PUT request to update a card expense by ID.

  async function updateExpense(
    client: BrexClient, 
    expenseId: string, 
    updateData: Omit<UpdateExpenseParams, 'expense_id'>
  ): Promise<UpdateExpenseResponse> {
    try {
      logDebug(`Updating expense with ID: ${expenseId}`);
      
      // Make API call to Brex to update the expense
      const response = await client.put(`/v1/expenses/card/${expenseId}`, updateData);
      
      // Validate the response
      if (!response || !response.id) {
        throw new Error("Invalid response from expense update request");
      }
      
      return response;
    } catch (error) {
      logError(`Failed to update expense: ${error instanceof Error ? error.message : String(error)}`);
      throw new Error(`Expense update failed: ${error instanceof Error ? error.message : String(error)}`);
    }
  }

• src/tools/index.ts:344-392 (schema)

  JSON input schema for the update_expense tool, as exposed in the MCP listTools response. Defines parameters, descriptions, and requirements.

  name: "update_expense",
  description: "Update an existing card expense",
  inputSchema: {
    type: "object",
    properties: {
      expense_id: {
        type: "string",
        description: "ID of the expense to update"
      },
      memo: {
        type: "string",
        description: "Memo text to attach to the expense (optional)"
      },
      category: {
        type: "string",
        description: "Category of the expense (optional)"
      },
      budget_id: {
        type: "string",
        description: "ID of the budget to associate with the expense (optional)"
      },
      department_id: {
        type: "string",
        description: "ID of the department to associate with the expense (optional)"
      },
      location_id: {
        type: "string",
        description: "ID of the location to associate with the expense (optional)"
      },
      custom_fields: {
        type: "array",
        description: "Custom fields to update (optional)",
        items: {
          type: "object",
          properties: {
            key: {
              type: "string",
              description: "Key of the custom field"
            },
            value: {
              type: "object",
              description: "Value of the custom field"
            }
          }
        }
      }
    },
    required: ["expense_id"]
  }

• src/tools/index.ts:50-50 (registration)

  Invocation of registerUpdateExpense to register the update_expense tool handler during tools initialization.

  registerUpdateExpense(server);

• src/tools/updateExpense.ts:114-155 (registration)

  Module-level registration function for the update_expense tool, called from index.ts to set up the handler.

  export function registerUpdateExpense(_server: Server): void {
    registerToolHandler("update_expense", async (request: ToolCallRequest) => {
      try {
        // Validate parameters
        const params = validateParams(request.params.arguments);
        logDebug(`Updating expense with ID: ${params.expense_id}`);
        
        // Get Brex client
        const brexClient = getBrexClient();
        
        try {
          // Extract the update data (everything except the expense_id)
          const { expense_id, ...updateData } = params;
          
          // Update the expense
          const updateResult = await updateExpense(brexClient, expense_id, updateData);
          
          logDebug(`Successfully updated expense with ID: ${updateResult.id}`);
          
          return {
            content: [{
              type: "text",
              text: JSON.stringify({
                status: "success",
                expense_id: updateResult.id,
                updated_at: updateResult.updated_at,
                expense_status: updateResult.status,
                updated_fields: Object.keys(updateData).filter(key => updateData[key as keyof typeof updateData] !== undefined),
                message: `Expense ${updateResult.id} was updated successfully.`
              }, null, 2)
            }]
          };
        } catch (apiError) {
          logError(`Error updating expense: ${apiError instanceof Error ? apiError.message : String(apiError)}`);
          throw new Error(`Failed to update expense: ${apiError instanceof Error ? apiError.message : String(apiError)}`);
        }
      } catch (error) {
        logError(`Error in update_expense tool: ${error instanceof Error ? error.message : String(error)}`);
        throw error;
      }
    });
  }