Pass back grades via LTI Assignment and Grade Services (AGS)

Steps

1. During an LTI 1.3 resource link launch, inspect the https://purl.imsglobal.org/spec/lti-ags/claim/endpoint claim in the id_token JWT; it provides the lineitems URL, the optional lineitem URL (if a single pre-created grade column exists), and the available scopes.
2. If no lineitem URL is provided and you need to create a grade column, POST a lineitem object (with label, scoreMaximum, and optional resourceId) to the lineitems URL using Content-Type: application/vnd.ims.lis.v2.lineitem+json.
3. Obtain a scoped Bearer token by making a JWT Bearer client assertion request to the platform's OAuth 2.0 token endpoint, requesting the scope https://purl.imsglobal.org/spec/lti-ags/scope/score; use the token endpoint URL from the platform's OIDC configuration.
4. POST the score to {lineitem_url}/scores using Content-Type: application/vnd.ims.lis.v1.score+json; the body must include userId (the learner's subject claim from the launch JWT), activityProgress (e.g., Completed), gradingProgress (e.g., FullyGraded), scoreGiven, scoreMaximum, and timestamp.
5. To read back results, GET {lineitem_url}/results using the scope https://purl.imsglobal.org/spec/lti-ags/scope/result.readonly; results are returned as application/vnd.ims.lis.v2.resultcontainer+json.
6. Store the lineitem URL alongside the LTI launch session so future score submissions reference the correct grade column without requiring a new launch.