Probes a remote gbrain MCP endpoint with bearer auth. POSTs initialize,
classifies failures into NETWORK / AUTH / MALFORMED with one-line
remediation hints, and runs a tools/list capability probe to detect
sources_add MCP support (forward-compat for when gbrain ships URL ingest).
Token consumed from GBRAIN_MCP_TOKEN env, never argv. Required to set
both 'application/json' AND 'text/event-stream' in Accept; that gotcha
costs 10 minutes of debugging when missed (regression-tested).
Live-verified against wintermute (gbrain v0.27.1).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Garry Tan