Auto detection of the subscription id

README.md

@@ -1,10 +1,10 @@
 # Azure Cost CLI
 
-This is a simple tool to get the cost of your Azure subscription. It uses the Azure Cost Management API to get the cost of your subscription. It can be used in a workflow to get the cost of your subscription and use it in subsequent steps.
+This is a simple command line tool to get the cost of your Azure subscription. It uses the Azure Cost Management API to get the cost and output the results to the console or JSON. E.g. so it can be used in a workflow to get the cost of your subscription and use it in subsequent steps.
 
 ![](screenshot.png)
 
-## How to install
+## Installation
 
 You can install this tool globally, using the dotnet tool command:
 
@@ -14,29 +14,57 @@ dotnet tool install --global azure-cost-cli
 
 ## Upgrading
 
-When there is a new version available, you can use the dotnet tool update command to upgrade:
+When there is a new version available on NuGet, you can use the `dotnet tool update` command to upgrade:
 
 ```bash
 dotnet tool update --global azure-cost-cli 
 ```
 
 With a `--version` parameter, you can specify a specific version to install. Use the `--no-cache` parameter to force a re-download of the package if it cannot find the latest version.
 
-## How to use
+## Usage
 
 You can invoke the tool using the `azure-cost` command. You can use the `--help` parameter to get a list of all available options.
 
 ```bash
 azure-cost --help
 ```
 
+Which will show:
+
+```
+USAGE:
+    Azure Cost [OPTIONS]
+
+EXAMPLES:
+    Azure Cost show -s 00000000-0000-0000-0000-000000000000
+    Azure Cost show -s 00000000-0000-0000-0000-000000000000 -o json
+
+OPTIONS:
+    -h, --help            Prints help information
+    -s, --subscription    The subscription id to use
+    -o, --output          The output format to use. Defaults to Console (Console, Json)
+    -t, --timeframe       The timeframe to use for the costs. Defaults to BillingMonthToDate. When set to Custom, specify the from and to dates using the --from and --to options
+        --from            The start date to use for the costs. Defaults to the first day of the previous month
+        --to              The end date to use for the costs. Defaults to the current date
+
+COMMANDS:
+    show    Show the cost details for a subscription
+```
+
+If you do not specify a subscription id, it will fetch the actively selected one of the `az cli` instead. 
+
+## Authentication
+
+To make the call to the Azure cost API, you do need to run this from a user account with permissions to access the cost overview of the subscription. Further more, it needs to find the active credentials and it does so by using the `ChainedTokenCredential` provider which will look for the `az cli` token first. Make sure to run `az login` (with optionally the `--tenant` parameter) to make sure you have an active session.
+
 ## To do
 
 - [x] Show time range the report is based on
 - [x] Open source it on GitHub!
 - [x] Show the forecasted cost
 - [ ] Set thresholds, so it can return an error code
 - [ ] Generate markdown, so you can include it in a workflow job summary
-- [ ] More options to set and filter
+- [ ] More options to set and filter on
 - [x] Validate date ranges
 - [x] Workflow to push to NuGet