A workflow for creating a new agent skill, a reusable set of instructions for a coding agent. It covers naming, structure, triggering rules, related skills, catalog registration, and validation.

Use it when adding a skill under .agents/skills/. It searches the skill catalog, checks how the skill fits with existing skills, drafts its description and instructions, registers it, and runs checks.

It helps ensure a new skill is discoverable, useful, and not duplicating an existing skill or belonging in the general agent instructions instead.

How deephaven/deephaven-mcp configures Claude Code and Codex

Reuse

Borrowing it

Nothing to install: this file belongs to deephaven/deephaven-mcp. 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/deephaven/deephaven-mcp/main/.agents/skills/skill-add/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/deephaven/deephaven-mcp

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/deephaven/deephaven-mcp/skill-add/github.svg)](https://agentmods.dev/skills/deephaven/deephaven-mcp/skill-add)

Your own site

<a href="https://agentmods.dev/skills/deephaven/deephaven-mcp/skill-add"><img src="https://agentmods.dev/badge/skills/deephaven/deephaven-mcp/skill-add/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/deephaven/deephaven-mcp/skill-add"><img src="https://agentmods.dev/badge/skills/deephaven/deephaven-mcp/skill-add.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,666 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	$0.00071	$0.01666
Opus 5.5	$0.00028	$0.00666
Sonnet 5.5	$0.00014	$0.00333
Haiku 4.5	$0.00007	$0.00167

Measured 1mo ago against content hash 713aa8bca6de, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

skill-add 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 1mo 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/skill-add/SKILL.md · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Add an Agent Skill

End-to-end workflow for creating a new skill at .agents/skills/<name>/SKILL.md. Wraps ref-skill-authoring-standards (structure) + ref-skill-effectiveness (content) + ref-agents-md-curation (decide whether the content belongs in AGENTS.md instead).

A new skill that no parent invokes is invisible. The Composition gate at step 2 is the most important step — run it before drafting anything.

Steps

Decide reference vs workflow. Apply ref-skill-authoring-standards Naming and the prefix rule. A workflow is a verb-noun action a human invokes directly. A reference is a noun-phrase standards document loaded by other skills.
Composition gate. Required first design step.
- Search the catalog .agents/skills/README.md for an existing skill that already covers this concern. If found, edit that skill instead. Stop here.
- Identify which existing skills the new skill will invoke (its children).
- Identify which existing skills will invoke the new skill (its parents).
- If the new skill would have exactly one parent and no independent trigger, it is a section of that parent. Inline it; do not create a new file.
- Apply ref-skill-authoring-standards Composition is the architecture extraction and merge triggers.
Decide skill vs AGENTS.md vs both. Apply ref-agents-md-curation What belongs in AGENTS.md and What does NOT belong in AGENTS.md. If the content fits both, pick the single source of truth and decide which file points to which.
Pick the name and prefix. Apply ref-skill-authoring-standards Naming and the prefix rule. The prefix rule answers one question: will any human ever invoke this skill directly? If yes (even occasionally), no prefix — even if other skills also reference it. If no, prefix with ref-.
- The name must be lowercase letters, numbers, and hyphens only, at most 64 characters, and identical to the directory name. The spec rejects anything else.
- A ref--prefixed skill also carries user-invocable: false (ref-skill-authoring-standards Frontmatter contract). Unprefixed workflows omit the key.

Read the full file on GitHub · 64 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.

1mo ago First seen · 64 lines · 71 tokens per session scan A 713aa8bca6de

Subscribe to this mod's changes

skill-add is a skill published in the GitHub repository deephaven/deephaven-mcp (5 stars, last pushed 2d ago), licensed Apache-2.0. It adds 71 tokens to every session and 1,666 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.

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deephaven-mcp: Skill for Claude Code