Build a CallToolResult whose structuredContent is value serialized via
vibe's serializeToJson. When content is null it defaults to a single
text block carrying the JSON string of value, mirroring the reflection
layer's toToolResult behaviour so a structured result also has a
human-readable content fallback for clients that ignore structuredContent.
Build a CallToolResult whose structuredContent is value serialized via vibe's serializeToJson. When content is null it defaults to a single text block carrying the JSON string of value, mirroring the reflection layer's toToolResult behaviour so a structured result also has a human-readable content fallback for clients that ignore structuredContent.