Ax is a TypeScript-first programming framework for building applications with large language models through typed generation, agents, workflows, and optimization tools. It is intended for developers who want one model for LLM programs across TypeScript, Python, Java, C++, Go, Rust, and other runtimes.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add ax-llm/ax --skill ax-typesafegit clone --depth 1 https://github.com/ax-llm/axWrote 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/skills/ax-llm/ax/ax-typesafe)<a href="https://agentmods.dev/skills/ax-llm/ax/ax-typesafe"><img src="https://agentmods.dev/badge/skills/ax-llm/ax/ax-typesafe/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/skills/ax-llm/ax/ax-typesafe"><img src="https://agentmods.dev/badge/skills/ax-llm/ax/ax-typesafe.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 | $0.00068 | $0.04025 |
| Opus 5.5 | $0.00027 | $0.01610 |
| Sonnet 5.5 | $0.00014 | $0.00805 |
| Haiku 4.5 | $0.00007 | $0.00402 |
Grade C, and why
ax-typesafe scanned grade C with 1 finding 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 yesterday.
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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- cspell:ignore noul --> How it starts
The opening of the file, as written. The whole thing — 350 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Typesafe / Jev with Ax (TypeScript)
Use name: 'typesafe' for the Typesafe System One API. Jev is the model family;
jev-latest is the default model. Use the Ax exports below when integrating with
Ax. Python, Java, C++, Go, and Rust also support the adapter and native client.
Use their generated ax-<language>-typesafe skills for native syntax and types.
Choose the Interface
| Need | Interface | Result |
|---|---|---|
| Required booleans and fixed classes | ai({ name: 'typesafe', ... }) with ax(...).forward() |
Ordinary signature-shaped values |
| PNG/JPEG images and localization (TypeScript) | ax(...) with image inputs and box outputs |
Coordinates, optional evidence |
| Probabilities, confidence, and rubric scoring | ax(...) with evidence fields |
Typed evidence in normal program results |
| Advanced structured criteria/state | typesafe(...).systemOne(...) |
Native request features |
| Decisions followed by prose or tool use | A Typesafe decision step followed by a generative provider | Explicitly composed program results |
A reply:string output requests freeform text and is unsupported by Typesafe.
An output team:class "support, billing" returns one of those two strings.
Numbers, even with min/max bounds, do not define native scoring rubrics.
Decision evidence and reranking
Use signature fields to access decision metadata with Jev, OpenAI Decisions, or a generative provider:
query:string, document:string ->
relevant:boolean(evidence, threshold 0.7),
category:class "support, billing"(evidence),
relevance:score "Irrelevant, Related, Partial answer, Direct answer"(evidence)
Boolean evidence contains value, probability, threshold, and provenance.
Class evidence contains value, a complete label-to-probability map, and
provenance. Score evidence contains a continuous value from zero to the last
rubric index, ordered levels, ordered probabilities, and provenance.
Native class and score results can also contain the provider's confidence.
A score without (evidence) returns only its numeric value. Existing scalar
boolean and class fields keep their existing behavior.
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.
- yesterday Changed · +60 lines · +6 tokens per session c2d335c9c15c
- 3d ago Changed 5e1fabeb9f7c
- 5d ago Changed · +61 lines · +7 tokens per session 9296464883c8
- 8d ago Changed 216986da03cb
- 9d ago Changed d4079474e6f5
- 10d ago Changed 2e363c79a4ad
- 16d ago Changed d8b8be32a8aa
- 19d ago Changed 2735197ca265
- 21d ago Changed efe5a9c1eab3
- 24d ago First seen · 229 lines · 55 tokens per session scan C e0782a634a8b
ax-typesafe is a skill published in the GitHub repository ax-llm/ax (2,967 stars, last pushed 2d ago), licensed Apache-2.0. It adds 68 tokens to every session and 4,025 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it C with 1 finding (hidden instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-18.
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