1. What is Proofline MCP?

Proofline is an open-source validation control plane for agentic data pipelines. It gives coding agents and AI-assisted engineering workflows an MCP tool that answers a question conventional job status cannot:

The pipeline job says “success”—but did the correct data actually land in the correct place?

Proofline compares observed pipeline behavior with deterministic invariants or a trusted reference and returns a structured evidence report: pass/fail, expected value, actual value, and diagnostic context. An agent can call it before accepting a generated pipeline change, approving a deployment, or reporting that a run is healthy.

The server currently exposes two tools:

2. Why does it exist?

AI coding agents can generate ingestion and transformation code quickly, but a syntactically valid change is not necessarily a semantically correct pipeline. Unit tests and orchestration status cover only part of the failure surface.

Proofline targets the semantic correctness gap in agentic data engineering:

• Silent-success failures: the orchestrator is green while an expected row, partition, polygon, or aggregate was never produced.

• Schema and data-contract drift: a generated transformation changes keys, cardinality, types, partitions, or null behavior without crashing.

• Behavioral regression: candidate output differs from a golden dataset or last-known-good implementation even though both jobs complete.

• Distributional drift: time buckets, geospatial areas, aggregates, and other population-level signals shift because of timezone, mapping, filtering, or join defects.

• Weak agent feedback loops: coding agents see logs and exit codes, but lack deterministic, machine-readable evidence explaining what invariant failed.

• Fragmented observability: orchestration metadata, worker status, database state, and output quality are checked independently instead of as one cross-system assertion.

• Unverifiable AI-generated changes: an agent proposes code without attaching a reproducible evaluation record that a human or another agent can audit.

In AI-platform terms, Proofline acts as an eval and guardrail at the data-pipeline boundary. MCP makes that eval callable by any compatible agent, while deterministic checks keep the final decision outside the language model. Proofline complements logs, traces, unit tests, and data observability; it does not replace them.

3. How does it work?

flowchart TD
    A["Agent changes pipeline"] --> B["Reference or evidence"]
    B --> C["Deterministic invariants"]
    C --> D["Structured proof report"]
    D --> E["MCP response"]
    E --> F{"Accept change?"}

1. The agent or automation supplies candidate output or an evidence envelope.

2. Proofline evaluates exact invariants: row counts, key sets, uniqueness, aggregates, distributions, write completion, shape presence, session parity, area drift, or Jaccard.

3. Each check records its expectation, observed value, status, and focused evidence.

4. The MCP tool returns an overall decision plus every individual check.

5. The caller can block acceptance on status: "fail" and use the evidence to diagnose or repair the pipeline.

Proofline's decision path is deterministic: the LLM chooses when to call the tool, but it does not decide whether a violated invariant passes.

Live product demo

The repository includes a real MCP demo client and a reproducible VHS recording specification. First verify the interaction directly:

python scripts/demo_live.py

The product video is a one-time documentation artifact, not a CI job. To record it locally, install VHS and FFmpeg, then run this command from the repository root:

vhs demo/proofline.tape

This records the real MCP stdio interaction as assets/proofline-demo.gif. The checked-in MP4 is derived from that recording with FFmpeg. Normal GitHub Actions remain dedicated to tests and benchmarks.

4. Setup instructions

Requires Python 3.11 or newer.

git clone https://github.com/Abhishek249/proofline-mcp.git
cd proofline-mcp

python -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

ruff check .
pytest

Run the local MCP server over stdio:

proofline-mcp

Example Cursor-compatible MCP configuration:

{
  "mcpServers": {
    "proofline": {
      "command": "/absolute/path/proofline-mcp/.venv/bin/proofline-mcp"
    }
  }
}

Restart the MCP client after changing its configuration. It should discover validate_candidate_pipeline and validate_geospatial_run.

Run the public proof and benchmark:

python scripts/prove_it.py
python scripts/benchmark_mcp.py --output benchmark-report.json

Docker users can build the stdio server with:

docker build -t proofline-mcp .
docker run --rm -i proofline-mcp

5. Results on NYC taxi-shaped trip data

The public benchmark generates deterministic taxi-shaped trips, executes a trusted reference and a candidate pipeline, and injects four known defect classes across four seeds and two dataset sizes. Every trial crosses a real MCP stdio client/server boundary.

View the successful GitHub Actions run · Read the permanent benchmark record

These results establish reproducibility for Proofline's published controlled fault model on a GitHub-hosted Ubuntu 24.04 runner with Python 3.12.14. They are not claims about arbitrary production pipelines. Validation against external, real-world geospatial infrastructure is a separate milestone.

Roadmap

• Deterministic reference/candidate framework

• Evidence-rich MCP tools

• Controlled fault injection

• Independent GitHub Actions proof and benchmark

• Reusable geospatial evidence contract

• Real public NYC TLC Parquet adapter

• Pluggable PostgreSQL and orchestration adapters

• Signed evidence bundles and OpenTelemetry traces

• Policy-gated pull-request integration

• Empirical evaluation and research paper

Proofline is an early research prototype and is not yet a production quality gate. Contributions, fault cases, and benchmark improvements are welcome.