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Money API Schema Validator
Build a developer tool that validates how monetary amounts are represented in APIs, SDKs, and service contracts. It would catch hidden precision, scale, currency, and rounding ambiguities before production, reducing high-cost integration failures.
Why this matters
You run a product where money crosses service boundaries, partner APIs, and reporting systems. Every team thinks they understand amounts until one side assumes two decimals, another assumes six, and a serializer silently changes meaning. The problem is not just storage; it is the contract between systems. Existing docs and style guides leave too much room for guesswork, especially when new engineers or generated code enter the loop. You need a tool that makes money fields explicit, tests those assumptions automatically, and blocks dangerous API changes before they become production incidents or reconciliation nightmares.
- · Built for Fintech engineering teams, payment platforms, treasury software vendors, and B2B SaaS companies that expose money-related APIs.
- · Most likely monetization: SaaS subscription.
The Pain · Narrative
You run a product where money crosses service boundaries, partner APIs, and reporting systems. Every team thinks they understand amounts until one side assumes two decimals, another assumes six, and a serializer silently changes meaning. The problem is not just storage; it is the contract between systems. Existing docs and style guides leave too much room for guesswork, especially when new engineers or generated code enter the loop. You need a tool that makes money fields explicit, tests those assumptions automatically, and blocks dangerous API changes before they become production incidents or reconciliation nightmares.
Score Breakdown
Market Signal
Go-to-Market
Engineering managers at startup and mid-market fintech companies with 5-50 developers shipping payment, wallet, lending, or ledger APIs
~15K-30K organizations globally
SEO long-tail
$199/month
10 teams install the CI linter and 3 convert to paid plans within 30 days
MVP Scope · 1–2 weeks
- Define a strict money schema spec covering amount, currency, scale, and rounding metadata
- Build an OpenAPI parser that detects money-like fields in API specs
- Create 15 lint rules for ambiguous amount representations
- Generate a CLI that outputs actionable validation errors
- Publish a landing page with example failures and email capture
- Add GitHub app support for pull request comments on schema violations
- Implement contract tests for cross-system precision mismatches
- Ship TypeScript and Python example SDK wrappers with safe money types
- Create a sample dashboard showing issue trends by repo and service
- Run outreach to 30 fintech engineering leads using the demo and trial
Differentiation
Why This Might Fail
Self-rebuttal — the most important trust signal
- 1Teams may treat this as a nice-to-have linting layer rather than a budget-worthy production control unless messaging ties directly to incident prevention.
- 2Large customers may require support for many custom schemas and legacy edge cases, making onboarding slower than expected.
- 3API platforms or schema tooling vendors could add basic money-field validation features and compress differentiation.
Evidence Summary
How AI synthesized this insight — no verbatim quotes
The strongest pattern in the discussion was extended debate about representing money safely across APIs. Roughly a dozen comments focused on strings versus integers versus decimal types, explicit scale, JSON precision limits, and partner mismatches. Several participants highlighted that implicit assumptions cause severe magnitude errors and that explicitness matters more than raw efficiency. That points to a real need for automated schema enforcement.
Action Plan
Validate this opportunity before writing code
Recommended Next Step
Build
Strong demand signals detected. Real pain, real willingness to pay — start building an MVP.
Landing Page Copy Kit
Ready-to-paste copy based on real Reddit community language — no editing required
Headline
Money API Schema Validator
Sub-headline
Build a developer tool that validates how monetary amounts are represented in APIs, SDKs, and service contracts. It would catch hidden precision, scale, currency, and rounding ambiguities before production, reducing high-cost integration failures.
Who It's For
For Fintech engineering teams, payment platforms, treasury software vendors, and B2B SaaS companies that expose money-related APIs
Feature List
✓ OpenAPI and JSON schema linting for money fields ✓ Precision and rounding rule validation across services ✓ Contract tests for partner-specific decimal expectations ✓ Language-specific SDK generation with safe money types ✓ CI checks and pull request annotations
Where to Validate
Share your landing page in r/HN · front_page — that's exactly where these pain points were discovered.
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