JSON message

Remember, generating a schema from a message is always an approximation. Try different options, modify both the JSON and the ASN.1 for the best match. See examples. Use asn1-playground to experiment with the schema.
Non-ASN.1 characters:

Underscores are not valid ASN.1 characters, but some ASN.1 compilers allow them.

Treat arrays as:

Inserting a NULL into an array requires more complex ASN.1.
Include ASN.1 value in the generated schema.
Generate default values for primitive types.
Show how the input JSON message can be changed to better fit ASN.1 schema rules.
Generate an exact, but more complex schema.
Add ASN.1 extension marker '...' to SEQUENCE/CHOICE to accommodate for new fields/versioning.
ASN.1 Schema