MobX Formkit is a form state management library that uses MobX observables to keep field values and form behavior reactive. It supports declarative fields, validation, nested structures, change tracking, events, and bindings for several UI frameworks and vanilla JavaScript.
Borrowing it
Nothing to install: this file belongs to foxhound87/mobx-formkit. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/foxhound87/mobx-formkit/master/AGENTS.mdgit clone --depth 1 https://github.com/foxhound87/mobx-formkitWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/foxhound87/mobx-formkit/agents-md)<a href="https://agentmods.dev/instructions/foxhound87/mobx-formkit/agents-md"><img src="https://agentmods.dev/badge/instructions/foxhound87/mobx-formkit/agents-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/foxhound87/mobx-formkit/agents-md"><img src="https://agentmods.dev/badge/instructions/foxhound87/mobx-formkit/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.07668 | $0.07668 |
| Opus 5.5 | $0.03067 | $0.03067 |
| Sonnet 5.5 | $0.01534 | $0.01534 |
| Haiku 4.5 | $0.00767 | $0.00767 |
Grade A, and why
mobx-formkit AGENTS.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 762 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Guide for AI Agents
A concise guide for LLMs working with MobX Formkit — the reactive MobX form state management library.
1. Project Identity
| Field | Value |
|---|---|
| Package | mobx-formkit |
| NPM | npmjs.com/package/mobx-formkit |
| GitHub | github.com/foxhound87/mobx-formkit |
| Docs | foxhound87.github.io/mobx-formkit |
| Version | 7.x (current: 7.1.0) |
| Size | ~8KB gzip (tree-shakeable) |
| License | MIT |
| Dependencies | MobX 5, 6 & 7 (peer: `^5.15.0 |
2. Philosophy
MobX Formkit is built on three core principles:
-
Reactive by default — Every field is a MobX observable. Form state (value, error, dirty, touched, etc.) is reactive. Your UI updates automatically with
observer()— no manualsetState, no change handlers to write. -
Composable by design — Fields nest infinitely (objects, arrays, arrays of arrays). Forms compose via
composer()for wizards and multi-step flows.ArrayMappreserves insertion order for dynamic lists. -
Plugin-driven validation — 8 validation drivers (DVR, VJF, AJV, YUP, JOI, ZOD, VALIBOT, VINEJS) share a uniform lifecycle. Swap or combine them without changing field definitions.
The result: you define your form structure declaratively, and reactivity, validation, change tracking, and UI bindings are automatic.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2mo ago First seen · 762 lines · 7,668 tokens per session scan A e775dcd013eb
mobx-formkit AGENTS.md is an instructions file published in the GitHub repository foxhound87/mobx-formkit (1,094 stars, last pushed yesterday), licensed MIT. It adds 7,668 tokens to every session, about $0.0307 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
mobx-formkit AGENTS.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| mobx-formkit AGENTS.mdfoxhound87/mobx-formkit | Instructions file | 1.1k | yesterday | MIT | A | 7,668 | Codex, OpenCode |
| vscode buildNext.instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 9,719 | GitHub Copilot |
| next.js AGENTS.mdvercel/next.js | Instructions file | 143k | today | MIT | A | 7,461 | Codex, OpenCode |
| langchain AGENTS.mdlangchain-ai/langchain | Instructions file | 149k | yesterday | MIT | A | 4,680 | Codex, OpenCode |
| vscode oss-third-party-notices.instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 5,516 | GitHub Copilot |
| vscode copilot-instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 3,093 | GitHub Copilot |
| deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness | Instructions file | 274k | 2d ago | MIT | A | 4,313 | Codex, OpenCode |