# AGENTS.md — Build guide for Finary ## Project scope Import holdings and liabilities from CSV, enter private-asset valuations, refresh permitted quotes and view dated net-worth/allocation snapshots. Catalogue verdict: kinda. The dashboard half of Finary is a weekend project: a table of holdings, a price fetcher, a few charts, a history table so you can see net worth over time. The hard half is the plumbing, connecting to hundreds of European banks and brokers through PSD2 aggregators, which needs either a licensed provider or a lot of scraping you do not want to maintain. You can get most of the way with CSV imports from your broker plus public price APIs for equities and crypto, refreshed on a cron. That gets you honest numbers with a monthly chore attached. If the chore is the reason you were paying, this is not a replacement. Use the implementation prompt below to define the deliverable. Complete each phase's acceptance checks before extending the scope. ## Working agreement - Inspect the repository and its existing instructions before choosing paths, dependencies or commands. Keep one coherent stack and explain changes to the proposed architecture. - Plan a vertical slice that accepts a real input and produces the useful output described below. Persist only the state the prompt calls for; respect memory-only and upstream-managed workflows. Use fixtures only when they are clearly labelled. - After scaffolding, document the actual install, development, check and build commands in README and keep them synchronized with the package or project manifest. Do not report commands as successful unless they ran. - Work in small steps. At handoff, list implemented flows, checks actually performed, remaining blockers, and any credentials or provider setup the owner must supply. - Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization. ## Prerequisites - Runtime and tools: TypeScript, React, Node, SQLite and decimal.js for explicit decimal calculations. - Before starting: A representative CSV with known totals, currency and date conventions, and an agreed calculation specification. ## Stack and architecture - TypeScript, React, Node, SQLite and decimal.js for explicit decimal calculations - Data design: Store Account, Instrument, Position, Liability, Quote and FXObservation; every valuation includes timestamp/currency/source, and stale or absent quotes are shown explicitly. - Setup: A representative CSV with known totals, currency and date conventions, and an agreed calculation specification ## Security and data integrity - Preserve imported source rows and units, use decimal arithmetic with stated rounding, and retain correction history. Missing values are unknown rather than zero; reports describe records and assumptions rather than giving advice. - No bank credentials, trading or personalized recommendations in the MVP. Distinguish contributions from investment returns and disclose valuation assumptions before charting performance. - Keep secrets outside client bundles and exported projects; document what leaves the device and make retention/deletion controls visible. ## Agent implementation rules - Project rule — domain: Store Account, Instrument, Position, Liability, Quote and FXObservation; every valuation includes timestamp/currency/source, and stale or absent quotes are shown explicitly. - Project rule — scope and recovery: No bank credentials, trading or personalized recommendations in the MVP. Distinguish contributions from investment returns and disclose valuation assumptions before charting performance. - Project rule — acceptance: Price one asset in EUR, retain another without a quote and add a USD liability; totals identify excluded/stale values and do not silently mix currencies. - Project rule — delivery: document real setup commands and permissions; do not claim a build, accuracy level, performance result or security certification that has not been demonstrated. ## Optional agent skills and references - Recommended skill: [web-design-guidelines](https://github.com/vercel-labs/agent-skills/blob/main/skills/web-design-guidelines/SKILL.md) — review keyboard access, focus, validation, error recovery and the readable work/review interface or HTML report. Follow the maintainer's installation instructions and match its requirements to the chosen runtime. - Recommended skill: [sharp-edges](https://github.com/trailofbits/skills/blob/main/plugins/sharp-edges/skills/sharp-edges/SKILL.md) — review configuration and API defaults against the app-specific invariants and recovery boundaries above; this is not a security certification. Follow the maintainer's installation instructions and match its requirements to the chosen runtime. Read the linked SKILL.md and its dependencies before adding a skill. Select only the skills matching this project's runtime and task; their documentation does not supply API access, credentials or approval to perform external actions. Pin the reviewed revision where the tool supports it. Follow the chosen agent's documented project-level installation mechanism. ## Distribution ideas These are optional planning notes. Obtain the owner's approval before publishing or contacting anyone. - Demonstrate this working slice using synthetic or explicitly authorized non-sensitive examples: Import holdings and liabilities from CSV, enter private-asset valuations, refresh permitted quotes and view dated net-worth/allocation snapshots. - Share a synthetic example export and the acceptance walkthrough; keep real customer, health, financial and source data private: Price one asset in EUR, retain another without a quote and add a USD liability; totals identify excluded/stale values and do not silently mix currencies. - State the limits before asking someone to replace their existing tool: No bank credentials, trading or personalized recommendations in the MVP. Distinguish contributions from investment returns and disclose valuation assumptions before charting performance. ## Engineering roadmap 1. Phase 1 — Pin the working slice and create its example input: Import holdings and liabilities from CSV, enter private-asset valuations, refresh permitted quotes and view dated net-worth/allocation snapshots. Confirm setup: A representative CSV with known totals, currency and date conventions, and an agreed calculation specification. 2. Phase 2 — Implement persistence and write-time invariants before decorating the UI: Store Account, Instrument, Position, Liability, Quote and FXObservation; every valuation includes timestamp/currency/source, and stale or absent quotes are shown explicitly. 3. Phase 3 — Connect the working view to real saved state. Preserve imported source rows and units, use decimal arithmetic with stated rounding, and retain correction history. Missing values are unknown rather than zero; reports describe records and assumptions rather than giving advice. 4. Phase 4 — Expose the app-specific limits and recovery path in context: No bank credentials, trading or personalized recommendations in the MVP. Distinguish contributions from investment returns and disclose valuation assumptions before charting performance. 5. Phase 5 — Walk through this concrete acceptance case and preserve its exported evidence: Price one asset in EUR, retain another without a quote and add a USD liability; totals identify excluded/stale values and do not silently mix currencies. Finish the README and backup/restore instructions; report unfinished capabilities explicitly. ## Paid-product capabilities outside this build - Automatic bank and broker sync across hundreds of institutions - Mobile apps with push updates and Face ID - Automated real estate valuation estimates and loan tracking - Benchmarking against other users and the community and content layer - Someone else fixing the connector the day your bank changes its API ## Implementation prompt Build the following focused alternative to Finary. This is a deliberately limited personal or small-team substitute, not parity with the paid service. WORKING SLICE Import holdings and liabilities from CSV, enter private-asset valuations, refresh permitted quotes and view dated net-worth/allocation snapshots. SETUP AND ARCHITECTURE Use TypeScript, React, Node, SQLite and decimal.js for explicit decimal calculations. Prerequisites: A representative CSV with known totals, currency and date conventions, and an agreed calculation specification. Before integrating anything, record actual versions and permissions, plus model files or provider limits only where used, in the README; make unavailable dependencies visible rather than simulating success. DOMAIN MODEL AND INVARIANTS Store Account, Instrument, Position, Liability, Quote and FXObservation; every valuation includes timestamp/currency/source, and stale or absent quotes are shown explicitly. IMPLEMENTATION CONTRACT Preserve imported source rows and units, use decimal arithmetic with stated rounding, and retain correction history. Missing values are unknown rather than zero; reports describe records and assumptions rather than giving advice. Provide an input/setup view, the main work view, and a review/export view appropriate to this workflow. Preserve the last saved state if a job or save fails. Include empty, loading, permission-denied, partial and retryable-error states. Log identifiers and error categories without secret values or unnecessary private content. APP-SPECIFIC BOUNDARY AND RECOVERY No bank credentials, trading or personalized recommendations in the MVP. Distinguish contributions from investment returns and disclose valuation assumptions before charting performance. ACCEPTANCE SCENARIO Price one asset in EUR, retain another without a quote and add a USD liability; totals identify excluded/stale values and do not silently mix currencies. Also reopen the app after an interrupted operation, confirm the saved record/export remains inspectable, and document the recovery action. These are implementation acceptance requirements, not a claim that this guide has been tested. DELIVERY Deliver a runnable repository with migrations or project-format versioning, a non-sensitive example, environment/permission setup, the exact manual acceptance steps, and a backup/export-and-restore walkthrough. Implement the working slice before optional integrations; list any deferred paid-product capabilities honestly. Do not add capabilities outside the working slice just to resemble the original product. PROJECT RULES FOR AGENTS.md Keep the domain invariants above executable at the write boundary. Propose scope changes before adding providers or permissions. Never fabricate source evidence, publish results, identity matches or successful delivery. Preserve user originals and require an explicit confirmation for destructive changes or external publication. ## Completion evidence Demonstrate the prompt's acceptance scenarios against the scoped workflow. Include setup from a clean checkout and failure recovery. Check persistence across restart and export/restore only for the state the prompt says to store; for memory-only tools, confirm that temporary content is discarded as specified. Record actual results and remaining limitations. A detailed plan alone does not establish a working replacement.