Open-source tools or schemas for durable portfolio data that LLMs can analyze?

Hi everyone! I’m looking for recommendations on how people structure long-term portfolio data outside of broker apps or SaaS dashboards.

I’m especially interested in workflows/tools that make portfolio data:

– portable and local-first

– readable as plain files, e.g. JSON/CSV/JSONL

– able to represent holdings, transactions, snapshots, asset metadata, and recurring tasks

– easy to audit over time

– structured enough for tools like Claude Code/Codex/LLMs to analyze safely

For example, instead of relying only on a broker UI or spreadsheet, I’m thinking about a canonical portfolio data layer that can later feed dashboards, analytics, reports, or imports/exports from IRS fillings, bank statements etc.

Are there any open-source tools, schemas, or workflows you recommend for this?

Do you use spreadsheets, some app, custom JSON, broker exports, or something else?

I’m also curious if anyone has had success making their investment data “LLM-friendly” for analysis, rebalancing checks, documentation, or planning workflows.