The DCMD_PROC_TIDSTATUS command returns a structure of type procfs_status, which is equivalent to debug_thread_t:

typedef struct _debug_thread_info {
  pid_t       pid;
  pthread_t   tid;
  uint32_t    flags;
  uint16_t    why;
  uint16_t    what;
  uint64_t    ip;
  uint64_t    sp;
  uint64_t    stkbase;
  uint64_t    tls;
  uint32_t    stksize;
  uint32_t    tid_flags;
  uint8_t     priority;
  uint8_t     real_priority;
  uint8_t     policy;
  uint8_t     state;
  int16_t     syscall;
  uint16_t    last_cpu;
  uint32_t    timeout;
  int32_t     last_chid;
  sigset_t    sig_blocked;
  sigset_t    sig_pending;
  siginfo_t   info;

  // blocking information deleted (see next section)

  uint64_t    start_time;
  uint64_t    sutime;
} debug_thread_t;

More information than you can shake a stick at (224 bytes)! Here are the fields and their meanings:

pid and tid
The process ID and the thread ID.
Flags indicating characteristics of the thread (see <sys/debug.h> and look for the constants beginning with _DEBUG_FLAG_).
why and what
The why indicates why the thread was stopped (see <sys/debug.h> and look for the constants beginning with _DEBUG_WHY_) and the what provides additional information for the why parameter. For _DEBUG_WHY_TERMINATED, the what variable contains the exit code value, for _DEBUG_WHY_SIGNALLED and _DEBUG_WHY_JOBCONTROL, what contains the signal number, and for _DEBUG_WHY_FAULTED, what contains the fault number (see <sys/fault.h> for the values).
The current instruction pointer where this thread is executing.
The current stack pointer for the thread.
stkbase and stksize
The base of the thread's stack, and the stack size.
The Thread Local Storage (TLS) data area. See <sys/storage.h>.
See <sys/neutrino.h> constants beginning with _NTO_TF.
priority and real_priority
The priority indicates thread priority used for scheduling purposes (may be boosted), and the real_priority indicates the actual thread priority (not boosted).
The scheduling policy (e.g. FIFO, Round Robin).
The current state of the thread (see <sys/states.h>, e.g., STATE_MUTEX if blocked waiting on a mutex).
Indicates the last system call that the thread made (see <sys/kercalls.h>).
The last CPU number that the thread ran on (for SMP systems).
Contains the flags parameter from the last TimerTimeout() call.
The last channel ID that this thread MsgReceive()'d on. Used for priority boosting if a client does a MsgSend() and there are no threads in STATE_RECEIVE on the channel.
sig_blocked, sig_pending, and info
These fields all relate to signals—recall that signals have a process aspect as well as a thread aspect. The sig_blocked indicates which signals this thread has blocked. Similarly, sig_pending indicates which signals are pending on this thread. The info member carries the information for a sigwaitinfo() function.
The time, in nanoseconds since January 1, 1970, that the thread was started. Useful for detecting thread ID reuse.
Thread's system and user running times (in nanoseconds).