I think your real issue is number vs string on sequence and ids. I will mock up a POST with your JSDON later today, but here is a valid sample for you to review in the mean time:
{
"emailSubject": "Test 3",
"emailBlurb": "Using two templates from composite template structure",
"brandId" : "f8c86e34-722e-4360-a9a0-54647bcd3004",
"status": "created",
"compositeTemplates": [{
"serverTemplates": [{
"sequence": "1",
"templateId": "6E558133-112C-434E-BF84-7C4DF340F042"
}],
"inlineTemplates": [{
"sequence": "1",
"recipients": {
"signers": [{
"email": "David.grigsby@docusign.com",
"name": "David W. Grigsby",
"recipientId": "1",
"roleName": "Role",
"tabs": {
"textTabs": [{
"value": "David Grigsby",
"tabLabel": "name"
},
{
"value": "David",
"tabLabel": "first_name"
}]
}
}]
}
}]
},
{
"serverTemplates": [{
"sequence": "2",
"templateId": "12C8894E-505C-480F-92FF-245DC387AD34"
}],
"inlineTemplates": [{
"sequence": "2",
"recipients": {
"signers": [{
"email": "David.grigsby@docusign.com",
"name": "David W. Grigsby",
"recipientId": "1",
"roleName": "Role",
"tabs": {
"textTabs": [{
"value": "David W. Grigsby",
"tabLabel": "name"
},
{
"value": "Grigsby",
"tabLabel": "last_name"
}]
}
}]
}
}]
}]
}