Create a custom tag at the project level, idempotently returning the tag if it already exists.
What this endpoint does
Creates a new custom tag at the project level in ASI. The tag name is provided as a path parameter and preserved with the casing given (filtering is case-insensitive). The operation is idempotent — calling with an existing tag name succeeds without error. Tags created here appear in ASI Tagging: Get Tags and can be applied to assets via ASI Tagging: Bulk Tag Assets. The project_id comes from GET https://api.securitytrails.com/v2/projects (undocumented on this site). Authentication: apikey header (ASI/SecurityTrails key).
Response data
Returns the standard ApiListResponse[CustomTagPublic] envelope: {"data": [{"title": "tag_name"}], "meta": {"counts": {"returned": 1, "total": 1}, ...}} containing the created or existing tag.