Clarify which search Skus are compatible (#642)

* Adding anchors

* Free wont work

Author: pamelafox

README.md

@@ -66,7 +66,7 @@ However, you can try the [Azure pricing calculator](https://azure.com/e/8ffbe5b1
 - Azure Blob Storage: Standard tier with ZRS (Zone-redundant storage). Pricing per storage and read operations. [Pricing](https://azure.microsoft.com/pricing/details/storage/blobs/)
 - Azure Monitor: Pay-as-you-go tier. Costs based on data ingested. [Pricing](https://azure.microsoft.com/pricing/details/monitor/)
 
-To reduce costs, you can switch to free SKUs for Azure App Service, Azure Cognitive Search, and Form Recognizer by changing the parameters file under the `infra` folder. There are some limits to consider; for example, you can have up to 1 free Cognitive Search resource per subscription, and the free Form Recognizer resource only analyzes the first 2 pages of each document. You can also reduce costs associated with the Form Recognizer by reducing the number of documents in the `data` folder, or by removing the postprovision hook in `azure.yaml` that runs the `prepdocs.py` script.
+To reduce costs, you can switch to free SKUs for Azure App Service and Form Recognizer by changing the parameters file under the `infra` folder. There are some limits to consider; for example, the free Form Recognizer resource only analyzes the first 2 pages of each document. You can also reduce costs associated with the Form Recognizer by reducing the number of documents in the `data` folder, or by removing the postprovision hook in `azure.yaml` that runs the `prepdocs.py` script.
 
 ⚠️ To avoid unnecessary costs, remember to take down your app if it's no longer in use,
 either by deleting the resource group in the Portal or running `azd down`.
@@ -144,7 +144,7 @@ If you already have existing Azure resources, you can re-use those by setting `a
 1. Run `azd env set AZURE_SEARCH_SERVICE_RESOURCE_GROUP {Name of existing resource group with ACS service}`
 1. If that resource group is in a different location than the one you'll pick for the `azd up` step,
   then run `azd env set AZURE_SEARCH_SERVICE_LOCATION {Location of existing service}`
-1. If the search service's SKU is not standard, then run `azd env set AZURE_SEARCH_SERVICE_SKU {Name of SKU}`. ([See possible values](https://learn.microsoft.com/azure/templates/microsoft.search/searchservices?pivots=deployment-language-bicep#sku))
+1. If the search service's SKU is not standard, then run `azd env set AZURE_SEARCH_SERVICE_SKU {Name of SKU}`. The free tier won't work as it doesn't support managed identity. ([See other possible values](https://learn.microsoft.com/azure/templates/microsoft.search/searchservices?pivots=deployment-language-bicep#sku))
 
 #### Other existing Azure resources
 

infra/main.bicep

@@ -18,6 +18,8 @@ param applicationInsightsName string = ''
 param searchServiceName string = ''
 param searchServiceResourceGroupName string = ''
 param searchServiceLocation string = ''
+// The free tier does not support managed identity (required) or semantic search (optional)
+@allowed(['basic', 'standard', 'standard2', 'standard3', 'storage_optimized_l1', 'storage_optimized_l2'])
 param searchServiceSkuName string // Set in main.parameters.json
 param searchIndexName string // Set in main.parameters.json