Azure devops pass build parameters through Rest API - rest

Question

I'm trying to pass a parameters through the build rest API using jira, but it doesn't override the parameter.
Pipeline:
parameters:
- name: "Testplan"
type: string
default: "NoPlanDefined"
stage: Test
jobs:
- job: Testing_And_Transfer
- task: PowerShell#2
displayName: "Testing API Call"
inputs:
targetType: 'filepath'
filePath: './script/Jira.ps1'
arguments:
-Jira_id ${{ parameters.Testplan }}
Jira.ps1 content:
Param(
[string]$Jira_id = "no ID"
)
#-----------------------Jira API--------------------------
echo 'This is a test \n ID: '
echo $Jira_id
My rest command is setup like so:
URL: https://dev.azure.com/{My corp}/MyHello/_apis/build/builds?api-version=6.0
Body:
{
"definition": {
"id": 1
},
"parameters": "{ \"Testplan\":\"Postman\" }"
}
When using the trigger, the ps1 return NoPlanDefined as expected.
When using a manual trigger and changing the parameter, the parameter
get changed as expected.
When trying to change the parameter through
the Rest api, Testplan is empty instead of Postman.
I'm I doing something wrong with the REST API?

Answer 1

That's because those are not parameters, despite the name used in the REST call. They are run-time variables, which behave differently and are available at a different scope than parameters.
There is a different API that allows you to specify templateParameters: https://learn.microsoft.com/en-us/rest/api/azure/devops/pipelines/runs/run-pipeline?view=azure-devops-rest-6.1

Answer 2

If you are familiar with PowerShell you can use the AzurePipelinesPS module and the command below to pass parameters to pipelines when invoking them.
$id = '2' # your pipeline id
$templateParameters = #{
Testplan = 'myTestPlan' # your parameter and value
}
Invoke-APPipeline -Instance https://dev.azure.com -Collection 'yourCollectionName' -Project 'yourProjectName' -ApiVersion '6.0-preview.1' -PipelineId $id -TemplateParameters $templateParameters
The module supports "sessions" to limit the number of required parameters. See the module's github page on how to create a session.