Support Schema Cycles

Is your feature request related to a problem? Please describe.
I am writing a custom MCP server that integrates with JIRA. The go-jira go project contains nice JIRA API data structures, such as jira.Issue. However, I cannot use jira.Issue with this library because cycles are not allowed for some reason:

output schema: ForType(jira.Issue): computing element schema: cycle detected for type jira.Issue

This is because JIRA Issues can reference other issues, hence the data structure can have references (pointers) to other Issues.

Describe the solution you'd like
Unless this is a fundamental constraint of MCP, I don't see why cycles are disallowed seeing as both golang and JSON support cyclic (self-referencing) schemas.

Describe alternatives you've considered
For now I've had to create a custom struct that replicates much of jira.Issue but without the cycles

Additional context
Add any other context or screenshots about the feature request here.

Start by tracing the schema generation path around the reported ForType(jira.Issue) cycle-detected error. Use the go-jira jira.Issue structure as a reproduction and add coverage showing that self-referencing schemas can be generated without the cycle error; done means the issue type is accepted while existing schema behavior remains intact.