ax-cpp-signature

ax-cpp-signature is a skill for Claude Code, Codex from ax-llm/ax. It costs 37 tokens per session (746 once invoked), scanned A, original, Apache-2.0.

A C++ guide for defining typed input and output contracts with the axllm library. These contracts describe the fields and data types that code, tools, or prompts accept and return.

In plain words
What is it for?
Use it to define string signatures, field descriptions, tool argument shapes, output schemas, and validation rules in axllm-based C++ code.
Why use it?
It helps keep data shapes explicit and supports JSON Schema output and validation, reducing mismatches between callers and results.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

About the project

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.

ax-llm/ax · 2,892 stars · on GitHub · axllm.dev

Install

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.

agentmods
npx agentmods add skills/ax-llm/ax/ax-cpp-signature
Any agent
npx skills add ax-llm/ax --skill ax-cpp-signature
Clone the repo
git clone --depth 1 https://github.com/ax-llm/ax

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for ax-cpp-signature

README.md
[![agentmods](https://agentmods.dev/badge/skills/ax-llm/ax/ax-cpp-signature.svg)](https://agentmods.dev/skills/ax-llm/ax/ax-cpp-signature)
Your own site
<a href="https://agentmods.dev/skills/ax-llm/ax/ax-cpp-signature"><img src="https://agentmods.dev/badge/skills/ax-llm/ax/ax-cpp-signature.svg" alt="Measured on agentmods" height="20"></a>
Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 746 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00037 $0.00746
Opus 5 $0.00018 $0.00373
Sonnet 5 $0.00007 $0.00149
Haiku 4.5 $0.00004 $0.00075

Measured 4d ago against content hash f6db041a1b02, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

ax-cpp-signature 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 4d 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.

packages/cpp/skills/ax-cpp-signature/SKILL.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Ax Signatures For C++

This skill helps an agent write C++ code with the generated Ax package axllm. Use the generated package API, examples, and manifests; do not import TypeScript-only APIs unless you are editing the TypeScript package.

When To Use

  • Declare input and output contracts with native generated-package APIs.
  • Generate JSON-schema-compatible shapes for outputs, tools, prompts, and validation.
  • Keep Standard Schema and TypeScript-only helper libraries out of generated-language code.

Package Facts

  • Language: C++.
  • Package: axllm.
  • Package API docs: API.md and axir-api.json.
  • Capability manifest: axir-capabilities.json.
  • Runnable examples: examples/.
  • Real network support: yes.
  • Scripted no-key transport support: yes.
  • Runtime profiles: javascript-quickjs, python-pyodide.

Core Pattern

#include "axllm/axllm.hpp"

auto sig = axllm::s("question:string -> answer:string");
auto schema = axllm::to_json_schema(axllm::Core::get(sig, "outputs"));

More Patterns

Simple string contract

Use the string form when field names and types are enough.

auto program = axllm::ax("questionText:string -> answerText:string");

Bounded class output

A class field constrains the model to a known label set.

auto router = axllm::ax(
    "messageText:string -> routeClass:class \"support, sales, engineering\"");

Native constraints

C++ exposes the generated record surface for constrained fields.

auto party_type = axllm::Core::record_new(
    "FieldType",
    axllm::object({
      {"name", "number"},
      {"minimum", 1},
      {"maximum", 12},
    }));

Validate and render

Validate the native record, then render its output fields as JSON schema.

axllm::Core::validate_signature(signature);
auto schema = axllm::to_json_schema(
    axllm::Core::get(signature, "outputs"),
    "outputs");

Reuse the signature

Pass the native signature record directly into AxGen.

axllm::AxGen program = axllm::ax(signature);
auto output = program.forward(client, inputs);

Read the full file on GitHub · 102 lines

Changes

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.

  1. 4d ago Changed f6db041a1b02
  2. 7d ago First seen · 102 lines · 37 tokens per session scan A 602751ec897a

Subscribe to this mod's changes

ax-cpp-signature is a skill published in the GitHub repository ax-llm/ax (2,892 stars, last pushed today), licensed Apache-2.0. It adds 37 tokens to every session and 746 once invoked, about $0.0002 per session on Opus 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.