What problem does it solve? Editing Power BI semantic model definitions directly as TMDL text files is error-prone: indentation is semantic, /// descriptions have strict placement rules, and some mistakes parse cleanly while silently corrupting the model. This Skill provides the syntax rules, property references, and known failure modes needed to safely author or fix .tmdl files when tools like Tabular Editor CLI or the Power BI MCP server are unavailable. ## Core Features & Use Cases - TMDL Syntax Guidance: Covers indentation depth rules, name quoting, /// descriptions versus // comments, property ordering, and multi-line DAX expression formatting for measures, columns, tables, relationships, roles, and calculation groups. - Property and Pattern References: Ships reference docs for all 30+ TMDL object types with valid enum values, column property rules (summarizeBy, formatString, PBI_FormatHint), and SQLBI naming conventions. - BIM-to-TMDL Conversion: Documents converting legacy model.bim (TMSL) to a TMDL definition/ folder via Tabular Editor CLI or the TOM TmdlSerializer. - Failure Mode Catalog: A gotchas reference documents silent corruption patterns, such as expression depth errors that delete format strings and calculation groups that break project loading without discourageImplicitMeasures. - Use Case: A developer needs to add a measure with a dynamic format string to a PBIP model under Git version control without opening Power BI Desktop; the Skill supplies the exact TMDL block, indentation depth, and the rule that formatString and formatStringDefinition cannot coexist. ## Quick Start Ask the agent to add a new measure with a description and format string to a table's .tmdl file in your PBIP project.
