malloy-discover

Data Discovery (Step 1, Silent)

CRITICAL: Read the model before writing ANY Malloy code. The model defines the sources, connection names, and fields. Never guess connection names.

Tool names are written bare here - get_context, execute_query, search_malloy_docs. The exact prefixed name depends on the host surface; match each against the tools you actually have.

PREREQUISITE: Make sure the Malloy MCP tools (get_context, execute_query, search_malloy_docs) are configured and reachable. If they are not, stop and resolve the MCP connection before continuing.

This step is silent. The agent does not present findings to the user yet. That happens in the next step (PROPOSE SCOPE). Silent does not mean unrecorded: append findings to your modeling workflow's modeling-notes.md as you go (grain proofs, key collisions, coverage cliffs, metadata drift, problems) so the scope proposal argues from a durable record rather than a reconstruction.

Profiling goes through Malloy. Even when the underlying engine is available directly (a duckdb CLI, psql, bq), run discovery queries through execute_query. The semantic layer under construction is the product, and grounded discovery through it is the point; profiling around it is a category error, not a shortcut: every finding would have to be re-verified through Malloy anyway.

Tools

• get_context: Ground yourself in the package's sources, views, and fields (with their docs). Call FIRST. The sources and their join paths are the schema you build on.
• execute_query: Run ad-hoc queries to preview data, verify values, check NULLs, validate assumptions.
• search_malloy_docs: Get Malloy syntax help when needed.

Workflow

1. Check for prior art signals                 → BI configs, metadata files, KPI docs, catalog
                                                 exports, READMEs, screenshots. Ask before using.
2. If BI config: read adapter reference        → Follow skill:malloy-lookml-review; read anything
                                                 else directly. Notes into modeling-notes.md
3. get_context                           → Ground yourself: sources, views, fields
4. Inspect source definitions                  → See ALL fields and join paths for key sources
5. Derive candidate joins/dimensions/measures  → Read them off the model and the data, not a suggestion tool
6. Define a minimal source if one is missing   → Just enough to run execute_query for previews
7. execute_query(query)                  → Preview data, verify values, check NULLs, check duplicates
8. search_malloy_docs(query)                    → Get syntax help when needed
9. Proceed to Step 2 (PROPOSE SCOPE)