In carrier networking, there is no error message that hasn’t been seen before. The answer is almost always in the manual.
The NSTV tool provides a range of troubleshooting tools and features, including: Carrier Network Service Tool V Manual
For the programmatic engineer, these pages are gold. RESTCONF/gRPC APIs are documented with request/response examples in JSON and Protobuf. The manual also includes a full OpenAPI 3.0 specification and reference Python libraries. A standout is Appendix D: “Writing Custom Remediation Playbooks” using an embedded Ansible-like engine. In carrier networking, there is no error message