malloy-discover

Profiles tables, columns, and relationships through Malloy queries before semantic modeling.

9|Updated Feb 16, 2026
One-click install
npx skills add https://github.com/mathisdrn/orca --skill malloy-discover-mathisdrn
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: malloy-discover
Source: https://github.com/mathisdrn/orca/tree/main/.agents/skills/malloy-discover
Command: npx skills add https://github.com/mathisdrn/orca --skill malloy-discover-mathisdrn

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Building a Malloy semantic model without understanding the underlying data leads to broken joins, wrong grains, and invalid measures. This Skill performs silent, query-grounded data discovery so every modeling decision is backed by actual data rather than schema guesses. ## Core Features & Use Cases - Grounded Profiling: Runs discovery queries through Malloy's execute_query tool to check NULL rates, cardinalities, distributions, and duplicate keys. - Join and Grain Validation: Verifies join cardinality, key value compatibility, and sibling tables at the same grain before proposing relationships. - Prior Art Detection: Detects LookML files, dbt projects, metadata files, and KPI docs, then reconciles their claims against queried data. - Use Case: Before writing a Malloy model for a new analytics database, run this discovery step to record table roles, data quality issues, and validated join paths in modeling-notes.md for the scope proposal. ## Quick Start Use the malloy-discover skill to silently profile the connected data sources and record findings in modeling-notes.md before proposing a model scope.

Frequently Asked Questions about malloy-discover

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I profile data before building a Malloy model?▼

Run discovery queries through Malloy's execute_query tool to check row counts, NULL rates, cardinalities, and distributions. Record findings in modeling-notes.md so the scope proposal is grounded in verified data rather than schema inference.

How to validate join cardinality in Malloy modeling?▼

Query foreign key uniqueness with a group_by and count aggregation, filtering for counts greater than one. This determines whether to use join_one or join_many and prevents fan-out that corrupts sum measures.

Does Malloy discovery work without a database connection?▼

Yes, in LookML-only mode the discovery step skips model reads and queries, using connection names and table paths extracted from LookML files instead. All proposals are flagged as unvalidated until a connection is available.

Why should profiling go through Malloy instead of direct SQL?▼

The semantic layer is the product being built, so findings from direct database access would need re-verification through Malloy anyway. Profiling through execute_query keeps discovery grounded in the actual modeling surface.

What data quality issues does Malloy discovery check?▼

It checks duplicate primary keys, denormalized count columns that conflict with joined aggregates, delimited list columns, mixed-grain summary rows, and mismatched join key values. Each issue is verified by query, not assumed from column names.