I would like to discover what tags exist in the specification so I can explore
requirements by theme. For example, “what tags are used?” helps me understand
how requirements are organized before I search for specific tags.
The user shall be able to retrieve a list of all tags used in the specification.
The MCP server shall expose a tool named list_all_tags that returns
all unique tags used across all requirements.
The response shall be a sorted list of unique tag strings.
Tags with subtags (e.g., “output:pdf”) shall be listed as complete tags,
not split into parts.
If no requirements have tags, an empty list shall be returned.