Auditing data warehouse health

This skill produces a project-wide audit of the data warehouse pipeline. Use it when the user wants a summary of everything broken, not a deep-dive on one sync. The deep-dive on individual failures is diagnosing-failed-warehouse-syncs; this skill is the scan that tells them where to look first.

When to use this skill

• "What's broken in my warehouse?" / "Give me a health check"
• "Audit my data pipeline"
• The user is new to a project and wants to know what they've inherited
• Weekly or monthly review of pipeline health
• Dashboards are stale and the user isn't sure which source is at fault

Available tools

Tool	Purpose
data-warehouse-data-health-issues-retrieve	One-shot: all failed/degraded items across the whole pipeline
external-data-sources-list	All sources with status and latest error
external-data-schemas-list	All schemas with status, last_synced_at, latest_error
view-list	All saved queries / materialized views with status and latest_error
view-run-history	Run history for a specific materialized view
external-data-sources-webhook-info-retrieve	Check per-source webhook state (not covered by data-health-issues)

The data-health-issues endpoint already aggregates across materializations, sync schemas, sources, batch export destinations, and transformations — it's the fastest path to a summary. Use the list endpoints when you need more context than the summary provides (row counts, non-failing items, schema-level detail).

What counts as an "issue"

The data-health endpoint returns items from five categories:

type	Trigger	Typical urgency
source	ExternalDataSource.status = Error — whole source connection broken	High
external_data_sync	schema in Failed or BillingLimitReached state (the data-health endpoint returns status: "failed" or status: "billing_limit" respectively)	Medium–High
materialized_view	DataWarehouseSavedQuery.is_materialized=true, status=Failed	Medium
destination	Batch export's latest run is FAILED / FAILED_RETRYABLE / TIMEDOUT / TERMINATED	Medium
transformation	HogFunction transformation in DISABLED / DEGRADED / FORCEFULLY_* state	Low–Medium

Each entry includes id, name, type, status, error, failed_at, url, and (for syncs/sources) source_type.

Note the data-health endpoint only reports active failures. It doesn't flag:

• Schemas paused by the user (should_sync = false)
• Non-materialized views with errors (only materialized views are reported)
• Schemas that are slow or stale but technically Completed
• Webhook problems on sync_type: "webhook" schemas. The bulk-sync safety net can succeed while the webhook push channel is silently broken (deregistered, disabled on the remote side, failing signature verification). These don't surface in data-health-issues — check per-source with webhook-info-retrieve.

If the user asks about staleness or unused items, reach beyond this endpoint — see Step 4.

Workflow

Step 1 — One-shot pull

Call data-warehouse-data-health-issues-retrieve. This returns every actively failing item in one request.

If the response is empty, tell the user their pipeline is healthy and stop. Don't invent problems.

Step 2 — Group and prioritize

Group the issues by type and sort within each group by severity:

1. Sources in Error first. A source failure cascades — every schema under it is effectively dead until the source reconnects. Fix these first.
2. Sync schemas next, in this order:
   • status: "billing_limit" entries (billing issue, non-technical — flag and route to billing)
   • Failed on heavily-used tables (user asks / check row counts via schemas-list if needed)
   • Failed on less-used tables
3. Materialized views. Usually independent of sources — a view failure is a HogQL or data issue in the view itself.
4. Batch export destinations. Affect data going out of PostHog — important but generally not blocking reads.
5. Transformations. Affect ingestion. Flag separately since these are HogFunction issues, not warehouse syncs.

Step 3 — Present the audit

Render a prioritized report. Don't dump the raw JSON — human-readable table per category:

## Data warehouse health — 7 issues

### 🔴 Sources (1)
- Stripe — authentication failed (failed 2h ago)
  → `diagnosing-failed-warehouse-syncs` on this source

### 🟠 Sync schemas (3)
- postgres_prod.orders (Failed 6h ago) — column "updated_at" does not exist
- postgres_prod.invoices (Failed 6h ago) — column "updated_at" does not exist
- hubspot.contacts (BillingLimitReached) — team quota exceeded

### 🟠 Materialized views (2)
- monthly_revenue — view failed (syntax error in HogQL)
- active_users_30d — view failed (missing table reference)

### 🟡 Destinations (1)
- S3 export "daily-events" (FAILED_RETRYABLE 3 runs in a row)

Recommended order:
1. Stripe auth (everything under it is dead)
2. Schema-drift on postgres_prod.orders / invoices — looks like upstream renamed a column
3. Billing limit on hubspot
4. Materialized views (independent — can be tackled any time)

The exact format is less important than: prioritized, grouped, actionable, and hinting at the right next skill.

Step 4 — Go beyond active failures (when asked)

If the user wants more than just "what's on fire" — e.g. "what else should I look at?" — cross-check:

Stale but "Completed" schemas: Call external-data-schemas-list and look for schemas with old last_synced_at relative to their sync_frequency. A schema on 1hour frequency that last synced 3 days ago is effectively broken even if status says Completed.

Unused materialized views: Call view-list. Materialized views cost storage and compute every run. If any are marked materialized but haven't been queried lately, surface them — cleaning-up-stale-warehouse-views territory (not yet implemented, but the data is available).

Sources with zero sync activity: Sources where every schema has should_sync: false or status = Paused. These were set up and then abandoned — candidates for cleanup via external-data-sources-destroy.

Broken webhooks on webhook-type schemas: Iterate the sources that have any schema with sync_type: "webhook" (visible via external-data-schemas-list). For each, call external-data-sources-webhook-info-retrieve({source_id}):

• exists: false while a schema is sync_type: "webhook" → webhook was never registered, or was deleted. Push channel is dead; only the bulk fallback is ingesting.
• external_status.error present → remote service is reporting a problem (permission revoked, endpoint deleted on their dashboard).
• external_status.status not "enabled" → remote has disabled the endpoint (often after repeated delivery failures).

Report these separately from the primary audit — they're a different shape of problem than the other categories, and the fix is a different skill (diagnosing-failed-warehouse-syncs scenario I, or setting-up-a-data-warehouse-source step 5.5).

Only run these extra checks if the user explicitly asks for a broader audit — they involve more tool calls and heuristics.

Step 5 — Offer the next step

End the audit with a clear hand-off:

• "Want me to dig into the Stripe failure?" → hands off to diagnosing-failed-warehouse-syncs
• "Want me to fix the schema drift on orders?" → hands off to tuning-incremental-sync-config
• "Want to disable the billing-capped schemas?" → one-click via external-data-schemas-partial-update

Never start applying fixes autonomously from an audit — the audit's job is to report and recommend, not remediate. Any fix should be confirmed explicitly before executing.

Example interaction

User: "Check the health of our data warehouse"

Agent:
- data-warehouse-data-health-issues-retrieve → 4 items
   [{type: "source", name: "Stripe", error: "401 Unauthorized", ...},
    {type: "external_data_sync", name: "postgres_prod.orders",
     error: "column \"updated_at\" does not exist", ...},
    {type: "materialized_view", name: "monthly_revenue",
     error: "syntax error at or near \"FORM\"", ...},
    {type: "destination", name: "S3 daily-events", error: "AccessDenied", ...}]

- Report:
  "Found 4 issues in your data warehouse:

   🔴 Sources (1)
   - Stripe — auth failure 2h ago (401). All 8 tables under it are currently dead.

   🟠 Sync schemas (1)
   - postgres_prod.orders — column `updated_at` was dropped on the source side,
     incremental sync can't find it.

   🟠 Materialized views (1)
   - monthly_revenue — HogQL syntax error ('FORM' instead of 'FROM').

   🟡 Destinations (1)
   - S3 export 'daily-events' — access denied on write.

   Suggest fixing in this order:
   1. Stripe credentials (unblocks everything under it)
   2. orders incremental-field drift
   3. monthly_revenue typo
   4. S3 permissions

   Want me to start on Stripe?"

Important notes

• The audit is read-only. Never call destructive tools from the audit flow. Hand off to the diagnosis/tuning skills — which in turn confirm before acting.
• Empty = healthy. Don't pad an empty audit with hypothetical issues. "No issues found" is a good answer.
• Source failures cascade. When reporting a source in Error, also mention which schemas under it are affected (or will be, once they try to sync again). The user needs to understand the blast radius.
• Billing limits aren't technical problems. Flag them but route to billing / quota discussion, not to a recovery action.
• Transformation issues are separate. HogFunctions aren't warehouse syncs — they show up in the audit because they're part of the broader pipeline, but they live in the posthog ingestion side. Route those to pipeline skills rather than trying to fix in-place here.
• data-health-issues only surfaces active failures. For staleness, unused views, or abandoned sources, you need to cross-check the list endpoints. Only do this when the user explicitly asks for a deeper audit.
• Webhook health is separate from schema health. The data-health endpoint doesn't know about webhook state. When a user's request mentions "real-time", "Stripe webhook", or "why is data hours behind on a webhook source", go straight to webhook-info-retrieve rather than inferring from schema status.