Desktop vs Service (What Changes)
MCP Engine can connect to either Power BI Desktop (a local PBIX you have open) or Power BI Service (a dataset via XMLA). Choosing the right target early avoids most "wrong model" mistakes.
When to pick which (practical decision guide)
Pick Desktop when you are developing locally - building new measures, testing schema changes, iterating on a model before publishing. Your PBIX is open in Power BI Desktop and you want changes to stay local until you save and publish. This is the typical workflow for solo development and prototyping.
Pick Service when you need to work against a shared, published dataset - for example, validating production KPIs, setting up workspace-level governance defaults, or running security tests against a centrally managed model. Service connections also give you workspace-scoped preferences that apply to all datasets in that workspace.
Key differences that affect your work
| Desktop | Service | |
|---|---|---|
| How changes persist | You must save the PBIX after MCP edits, or changes are lost | Changes are live immediately and can affect other users |
| Undo safety net | Close PBIX without saving to discard all changes | Use checkpoints/rollback (Pro) or restore from a backup |
| Workspace preferences | Not available (Desktop has no workspace concept) | Available with Pro tier - shared conventions across datasets |
| RLS testing | Role-based testing | Role-based + effective user identity (tier-gated) |
| Who can use it | Anyone with the PBIX file | Requires XMLA-capable workspace + authentication |
Practical gotcha: save your PBIX
The most common mistake with Desktop: you do 30 minutes of measure authoring through MCP, then close Power BI Desktop without saving. Everything is gone. The MCP server does not auto-save your PBIX.
Repeatable connections (stable IDs)
For Service, listing workspaces before datasets helps the server use stable identifiers (workspace GUID-based) so "connect to X again tomorrow" is reliable.
"List workspaces first, then list datasets in workspace 'Finance', then ask me which one to connect to."