What is agent-extension-standards?

A reference guide to the current extension formats used by Codex, Claude Code, and Agent Skills, including plugins, marketplaces, and skill directories.

Designing and checking harness adapters, plugin and marketplace manifests, skill folders, instruction-file bridges, configuration scopes, and extension lifecycle behavior.

It helps prevent mixing incompatible rules or relying on outdated assumptions when building or reviewing agent extensions.

agent-extension-standards — Skill for Codex by nklisch/skilltap

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.

Any agent

npx skills add nklisch/skilltap --skill agent-extension-standards

Clone the repo

git clone --depth 1 https://github.com/nklisch/skilltap

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/nklisch/skilltap/agent-extension-standards/github.svg)](https://agentmods.dev/skills/nklisch/skilltap/agent-extension-standards)

Your own site

<a href="https://agentmods.dev/skills/nklisch/skilltap/agent-extension-standards"><img src="https://agentmods.dev/badge/skills/nklisch/skilltap/agent-extension-standards/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/nklisch/skilltap/agent-extension-standards"><img src="https://agentmods.dev/badge/skills/nklisch/skilltap/agent-extension-standards.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 606 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 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.

Model	Per session	Once invoked
Fable 5.1	$0.00081	$0.00606
Opus 5.5	$0.00032	$0.00242
Sonnet 5.5	$0.00016	$0.00121
Haiku 4.5	$0.00008	$0.00061

Measured 2mo ago against content hash 81bc06fe0d35, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

agent-extension-standards 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.

.agents/skills/agent-extension-standards/SKILL.md · 54 lines

How it starts

The opening of the file, as written. The whole thing — 54 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Extension Standards

Ground extension work in the current research substrate. Do not reuse remembered Claude-only marketplace assumptions or flatten the two harnesses into a generic plugin format.

Load the applicable contract

Read .research/analysis/briefs/current-agent-extension-standards.md before making an architectural or behavioral decision in this domain.

Load a specialist brief when exact native details matter:

Codex: .research/analysis/campaigns/marketplace-standards/specialists/codex.md
Claude Code: .research/analysis/campaigns/marketplace-standards/specialists/claude.md
Agent Skills: .research/analysis/campaigns/marketplace-standards/specialists/agent-skills.md

Use attestations under .research/attestation/ for source-direct verification. Treat specialist briefs and the parent synthesis as analytical guidance, not primary sources. Never cite .research/.import-holding/ as evidence.

Preserve these boundaries

Treat a skill as its complete directory with top-level SKILL.md. Never manage only the Markdown file when sibling resources exist.
Use .agents/skills/ as skilltap's canonical portable placement when the skill is compatible. Create harness-native links or copies through adapters.
Keep Codex and Claude plugin manifests, catalogs, identities, caches, scopes, consent, and update semantics distinct.
Prefer deterministic native marketplace and plugin operations. Do not mutate a native plugin cache as an installation API.
Keep ~/AGENTS.md as skilltap's canonical global instruction file and model ~/.codex/AGENTS.md and ~/.claude/CLAUDE.md as native bridges, including their precedence and divergence hazards.
Separate desired skilltap state, native declared state, and effective installed state.
Classify transfer as faithful, materializable, partial, or blocked. Surface material consequences for piecewise operation-scoped approval.
Register only sources selected by the user. Do not add search, browsing, ranking, recommendation, or inventory-discovery behavior.

Read the full file on GitHub · 54 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.

agents/openai.yaml 246 B

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.

2mo ago First seen · 54 lines · 81 tokens per session scan A 81bc06fe0d35

Subscribe to this mod's changes

agent-extension-standards is a skill published in the GitHub repository nklisch/skilltap (7 stars, last pushed 1mo ago), licensed MIT. It adds 81 tokens to every session and 606 once invoked, about $0.0003 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 2026-08-31.

Building agents agent-skills ai-agents bun claude cli codex

agent-extension-standards next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
agent-extension-standardsnklisch/skilltap	Skill	7	1mo ago	MIT	A	81	Codex
imaging-data-commonssynthetic-sciences/openscience	Skill	4.3k	2d ago	Apache-2.0	A	62	Claude Code, Codex
flow-cytometry-analysissynthetic-sciences/openscience	Skill	4.3k	2d ago	Apache-2.0	A	67	Claude Code, Codex
molecular-cloningsynthetic-sciences/openscience	Skill	4.3k	2d ago	Apache-2.0	A	70	Claude Code, Codex
datamolsynthetic-sciences/openscience	Skill	4.3k	2d ago	Apache-2.0	A	67	Claude Code, Codex
shapsynthetic-sciences/openscience	Skill	4.3k	2d ago	Apache-2.0	A	109	Claude Code, Codex
genomic-intelligencesynthetic-sciences/openscience	Skill	4.3k	2d ago	Apache-2.0	A	150	Claude Code, Codex