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Your Tableau published data sources carry the calculated fields, relationships, and LOD expressions your analysts rely on — and workbooks carry even more. Credible reads both, re-expresses the calculations as Malloy, and — where you connect it — validates them against Tableau’s own query service.

What Credible Reads

Your published data sources (.tds / .tdsx) — calculated fields, default aggregations, folders, and the logical/physical data model — plus the calculated fields embedded in workbooks (.twb). These files are all the agent needs to translate. Connecting the official Tableau MCP server (tableau/tableau-mcp, hosted at mcp.tableau.com) is optional: it reads model metadata via the Metadata API and validates through the VizQL Data Service.

What Comes Across

The everyday modeling carries over. Here’s how the bigger pieces land — and where they get better:

The Migration Flow

Credible reads the data source and workbook calcs, translates fields and relationships to Malloy, enriches with #(doc)/#(index) tags, and — where you connect it — validates row-by-row against the VizQL Data Service.

What Credible Handles

  • LOD expressions encode a grain independent of the viz. A { FIXED [Customer ID] : SUM([Amount]) } becomes a Malloy aggregate at an explicit grain. Credible also distinguishes “real” LODs from workaround LODs that only existed to dedupe joins — the latter are unnecessary in a clean model.
  • Table calculations run over the rendered viz and depend on Compute-Using direction. They’re reconstructed as explicit Malloy window functions with a declared partition_by/order_by; TOTAL() maps to all().
  • Workbook-embedded calculated fields — business logic frequently lives in .twb, not the published .tds, so Credible scans both.
  • Viz-level formatting — Compute-Using direction, table layout, cosmetic styling — is presentation and is dropped; threshold-based color rules become model logic, and model-worthy defaults and labels carry over.

Before & After

Tableau calculated fields as authored against a data source:
A FIXED LOD becomes an aggregate declared at its grain; table calcs become explicit window calculations. Purely visual constructs — Compute-Using direction, quick table calcs, worksheet formatting — have no model equivalent and are dropped. More than a reformat. Logic that lived inside workbooks becomes a reusable, AI-discoverable model that serves every surface, not just Tableau — and Malloy’s symmetric aggregates keep totals correct where Tableau needed LODs to avoid double-counting. See what you gain →

Next Steps

Migration Overview

The method behind every migration

Metadata & Discovery

Tune your migrated model for AI retrieval