xint-three-phase-credential-unlock-model

xint capabilities are unlocked in three phases: Phase 1 (xAI API key only — 8 commands: analyze, ai-search, report, article, collections, costs, health, capabilities), Phase 2 (+ X_BEARER_TOKEN — 11 commands: search, profile, tweet, thread, trends, watch, stream, media, users, reposts), Phase 2b (+ X_CLIENT_ID + xint auth setup — 17 command families: engagement, analytics, growth, moderation, bookmark KB). MCP tiers must align to credential phases: OAuth-gated write tools belong in engagement tier, not read_only.