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Why Operator ETL?

The short answer: Most “AI + data” demos connect a chatbot to your warehouse. That fails FOIA and public-comment workflows for three predictable reasons — PII leaks, hallucinated counts, and runs you cannot replay. Operator ETL fixes each with a boundary you can test.

Prove it yourself: git clone → make e2e → WALKTHROUGH.md

The chatbot trap

flowchart TB
  subgraph bad [Typical AI ETL demo]
    User[Analyst asks chatbot]
    LLM[LLM with SQL tool]
    WH[(Full warehouse)]
    User --> LLM
    LLM --> WH
    LLM --> Memo[Leadership memo]
  end

  subgraph risks [What goes wrong]
    R1[PII in prompt context]
    R2[999 comments invented]
    R3[No audit trail]
  end

  Memo --> risks
Failure mode Real-world consequence
PII in context Email/phone from comment bodies reach the model before redaction review
Hallucinated KPIs Memo says “999 comments” — number not in any table; indefensible under audit
Opaque runs Cannot answer what ran, when, on which file for oversight or FOIA

The Operator ETL pattern

Separate what must be deterministic from what may be agentic.

flowchart TB
  subgraph data [Data plane — Python and SQL only]
    In[CSV / API intake]
    B[bronze immutable]
    S[silver validated]
    Q[quarantine bad rows]
    G[gold SQL marts]
    In --> B --> S
    B --> Q
    S --> G
  end

  subgraph policy [Policy plane — before any agent]
    PII[PII scan + vault]
    B --> PII
    PII --> S
  end

  subgraph control [Control plane — bounded agents]
    Graph[LangGraph]
    MCP[MCP allowlist 3 tools]
    Critic[critic faithfulness]
    Graph --> MCP
    MCP --> G
    Graph --> Critic
    Critic --> Insight[Verified insight]
  end
Layer Job Why it matters
Data Medallion ETL, idempotent ingest, quarantine Audit trail; bad rows never silently become KPIs
Policy PII scan, token vault, fail-closed gates Agents never see raw emails/phones
Control LangGraph + MCP + critic Orchestration without warehouse keys or invented numbers

Medallion = audit trail

FOIA officers need to show what arrived, what was rejected, and what was released.

flowchart LR
  Drop[File drop] --> Bronze[bronze_raw<br/>immutable hash]
  Bronze --> Silver[silver_comments<br/>Pydantic valid]
  Bronze --> Quarantine[quarantine_comments<br/>explicit errors]
  Silver --> Gold[gold_comment_kpis<br/>SQL aggregates]
  • Bronze never changes — replay and legal discovery friendly
  • Quarantine preserves bad rows with reasons — no silent drops
  • Gold is SQL-only — numbers agents and dashboards cite

Source: Databricks Medallion Architecture · Proof: tests/test_pipeline.py

Critic = defensible memos

Even template insights must not invent numbers. The critic extracts every integer from the draft and checks it against gold.

flowchart LR
  Gold[gold marts] --> Draft[insight draft]
  Draft --> Critic{critic}
  Critic -->|all numbers in gold| Pass[persist insight]
  Critic -->|999 not in warehouse| Fail[retry or HITL]

Example from the FOIA demo:

10 comments across 2 dockets… PII rate 0.4

Every number is verified before persist. Hallucinated 999 is rejected in tests/test_critic.py.

MCP = least privilege for agents

Agents do not get SELECT * FROM bronze. They get three typed tools:

flowchart LR
  Agent[AI agent] --> MCP[MCP server]
  MCP --> T1[get_gold_metrics]
  MCP --> T2[run_quality_sql]
  MCP --> T3[get_run_status]
  MCP -.->|denied| Vault[vault_decrypt]
  MCP -.->|denied| Raw[ad-hoc SQL]

Source: Model Context Protocol · Proof: tests/test_mcp_tools.py

What we prove today (and what we don't)

Claim Status Verify
FOIA pipeline on laptop Proven make e2e
PII not in insight output Proven 41 pytest
Critic rejects bad numbers Proven tests/test_critic.py
Live GCP / BigQuery E2E Partial Terraform scaffold only
Optional LLM insights Partial Mocked in CI; template default — LLM.md
Presidio PII Specified Regex scanner today

Full audit: FINAL-REVIEW.md

Who should care

You are… Start here
FOIA / program officer FOIA-Public-Comments-Guide.md
Engineer evaluating architecture HOW-IT-WORKS.md → white paper
Skeptic who wants proof WALKTHROUGH.md
Hiring manager / reviewer README → make e2e → FOUNDATIONS.md proof matrix

Open source

Apache License 2.0 — clone, fork, and run the proof gate. Sample data is synthetic; do not commit real FOIA records.

See also