Function schemaForMessageWithVisited

internal/mcp/schema.go:35–52

schemaForMessageWithVisited recurses into nested message fields while guarding against cycles. The descriptor full-name is the visit key — well-known types like google.protobuf.Value reference themselves via repeated-Value lists, which would stack-overflow without this. On a re-visit we emit an opa

(md protoreflect.MessageDescriptor, visited map[protoreflect.FullName]struct{})

// type (it can pass any JSON object; the server validates at the proto
// layer via protovalidate).
func schemaForMessageWithVisited(md protoreflect.MessageDescriptor, visited map[protoreflect.FullName]struct{}) jsonSchema {
	if _, seen := visited[md.FullName()]; seen {
		return jsonSchema{Type: "object"}
	}
	visited[md.FullName()] = struct{}{}
	defer delete(visited, md.FullName())

	root := jsonSchema{
		Type:       "object",
		Properties: map[string]jsonSchema{},
	}
	fields := md.Fields()
	for i := 0; i < fields.Len(); i++ {
		f := fields.Get(i)
		root.Properties[string(f.Name())] = schemaForField(f, visited)
	}
	return root
}

func schemaForField(f protoreflect.FieldDescriptor, visited map[protoreflect.FullName]struct{}) jsonSchema {
	// repeated → JSON array