EGC: Skill for Codex

.agents/skills/product-capability/SKILL.md

product-capability is a skill for Codex from Fmarzochi/EGC. It costs 60 tokens per session (906 once invoked), scanned A, a copy of product-capability, Apache-2.0.

A planning guide that turns product ideas or requirements documents into explicit engineering requirements before coding starts.

In plain words
What is it for?
Use it to define data rules, system interfaces, lifecycles, policies, and other conditions that an implementation must satisfy.
Why use it?
It exposes hidden assumptions, constraints, and unresolved decisions when a feature spans several services, codebases, or teams.

Skill for Codex

Written for Codex: agents/openai.yaml present. Also seen: installed under .agents/ (shared by several agents); mentions Codex; mentions OpenCode.

This is Fmarzochi/EGC's own configuration. It tells Codex how to work on EGC itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything EGC configures →

Reuse

Borrowing it

Nothing to install: this file belongs to Fmarzochi/EGC. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/Fmarzochi/EGC/main/.agents/skills/product-capability/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/Fmarzochi/EGC

Made for: 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 product-capability

README.md
[![agentmods](https://agentmods.dev/badge/skills/fmarzochi/egc/product-capability/github.svg)](https://agentmods.dev/skills/fmarzochi/egc/product-capability)
Your own site
<a href="https://agentmods.dev/skills/fmarzochi/egc/product-capability"><img src="https://agentmods.dev/badge/skills/fmarzochi/egc/product-capability/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.

agentmods 80×15 button for product-capability

Your own site · 80×15
<a href="https://agentmods.dev/skills/fmarzochi/egc/product-capability"><img src="https://agentmods.dev/badge/skills/fmarzochi/egc/product-capability.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 906 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 97% copy Near-identical to another mod 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 $0.00060 $0.00906
Opus 5 $0.00030 $0.00453
Sonnet 5 $0.00012 $0.00181
Haiku 4.5 $0.00006 $0.00091

Measured 9d ago against content hash e958cc974cc1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

product-capability 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 9d 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.

Origin

This is a copy

97% identical to product-capability — 8 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/product-capability/SKILL.md · 141 lines

How it starts

The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Product Capability

This skill turns product intent into explicit engineering constraints.

Use it when the gap is not "what should we build?" but "what exactly must be true before implementation starts?"

When to Use

  • A PRD, roadmap item, discussion, or founder note exists, but the implementation constraints are still implicit
  • A feature crosses multiple services, repos, or teams and needs a capability contract before coding
  • Product intent is clear, but architecture, data, lifecycle, or policy implications are still fuzzy
  • Senior engineers keep restating the same hidden assumptions during review
  • You need a reusable artifact that can survive across harnesses and sessions

Canonical Artifact

If the repo has a durable product-context file such as PRODUCT.md, docs/product/, or a program-spec directory, update it there.

If no capability manifest exists yet, create one using the template at:

  • docs/examples/product-capability-template.md

The goal is not to create another planning stack. The goal is to make hidden capability constraints durable and reusable.

Non-Negotiable Rules

  • Do not invent product truth. Mark unresolved questions explicitly.
  • Separate user-visible promises from implementation details.
  • Call out what is fixed policy, what is architecture preference, and what is still open.
  • If the request conflicts with existing repo constraints, say so clearly instead of smoothing it over.
  • Prefer one reusable capability artifact over scattered ad hoc notes.

Inputs

Read only what is needed:

  1. Product intent
    • issue, discussion, PRD, roadmap note, founder message
  2. Current architecture
    • relevant repo docs, contracts, schemas, routes, existing workflows
  3. Existing capability context
    • PRODUCT.md, design docs, RFCs, migration notes, operating-model docs
  4. Delivery constraints
    • auth, billing, compliance, rollout, backwards compatibility, performance, review policy

Core Workflow

1. Restate the capability

Read the full file on GitHub · 141 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 9d ago First seen · 141 lines · 60 tokens per session scan A e958cc974cc1

Subscribe to this mod's changes

product-capability is a skill published in the GitHub repository Fmarzochi/EGC (49 stars, last pushed today), licensed Apache-2.0. It adds 60 tokens to every session and 906 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to product-capability, differing in 8 lines, and is treated as a copy.

Related

Other skills, from other repositories