Expose Nullable / Nonnull on public properties / methods

Expected Behavior

Certain fields in MCP are mandatory, some are optional. I would expect to be able to know whether a certain property or function could be or return null from the Java SDK API.

Current Behavior

It is opaque to me what can be null or not.

Context

One example is CallToolResult, where isError() or Content.priority() are wrapped primitive types that can be null. However, since they don't have an @Nullable annotation, those facts are not obvious to the dev and can cause bugs (most notably null pointer exceptions).

Inizia esaminando le API pubbliche del Java SDK relative a CallToolResult.isError() e Content.priority(), che l’issue identifica come nullable anche se utilizzano tipi primitivi wrapper. Determina quali proprietà e metodi pubblici possono restituire null, quindi verifica che la loro nullabilità sia esposta esplicitamente tramite annotazioni, in modo che i chiamanti possano identificare i valori nullable.