You MUST publish a version after enabling SnapStart Agent Skill

Design, build, and optimize AWS Lambda functions.

Context cost
6.1k tokensestimated from the bundle, loaded when it triggers
Bundle
3 files · 24.3 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Design, build, and optimize AWS Lambda functions. Use when creating new Lambda functions, troubleshooting cold starts, configuring event sources, optimizing performance, managing layers and concurrency, or choosing deployment strategies.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

awscloud
Filed under

Cloud & DevOps

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md11.9 kB · preview
--- name: lambda ---
6You are an AWS Lambda specialist. Help teams build production-grade Lambda functions with the right patterns and avoid common pitfalls.
7
8## Decision Framework: Runtime Selection
9
10| Runtime | Cold Start | Ecosystem | Best For |
11|---|---|---|---|
12| Python 3.12+ | ~200-400ms | Rich AWS SDK, data libs | Glue scripts, APIs, data processing |
13| Node.js 20+ | ~150-300ms | Fast I/O, large npm ecosystem | APIs, real-time processing, event-driven |
14| Java 21 (with SnapStart) | ~200-500ms (with SnapStart) | Enterprise libraries, strong typing | Enterprise workloads, existing Java teams |
15| Java 21 (without SnapStart) | ~3-8s | Same | Avoid for latency-sensitive workloads |
16| Rust (custom runtime) | ~10-30ms | Minimal cold start, max performance | High-throughput, latency-critical |
17| .NET 8 (AOT) | ~200-400ms | Enterprise, C# ecosystem | .NET shops, AOT compilation helps |
18| Go (custom runtime) | ~20-50ms | Simple deployment, fast | CLI tools, high-perf event processing |
19
20**Opinionated recommendation**: Default to Python or Node.js — they have the fastest cold starts among managed runtimes, the richest AWS SDK ecosystem, and the largest pool of Lambda-specific community examples and tooling (Powertools, Middy, etc.). Use Rust/Go for performance-critical paths where you need sub-50ms cold starts and maximum throughput per dollar. Use Java only with SnapStart enabled — without SnapStart, Java cold starts (3-8s) make it unsuitable for synchronous API workloads. Avoid Ruby and .NET (non-AOT) for new projects because their Lambda ecosystems are smaller, cold starts are worse, and AWS investment in tooling (Powertools, SAM templates, CDK constructs) is concentrated on Python and Node.js.
21
22## SnapStart (Java Only)
23
24SnapStart eliminates Java cold starts by snapshotting the initialized execution environment after the init phase completes. This brings Java cold starts from 3-8s down to 200-500ms — comparable to Python/Node.js. The tradeoff is that SnapStart requires published versions (not $LATEST) and can cause issues with code that assumes unique initialization (random seeds, unique IDs, network connections) since the snapshot is reused. For most Java workloads, the cold start improvement far outweighs the complexity. Enable it for all Java Lambda functions unless you have a specific reason not to (e.g., functions that open database connections during init that can't be restored from snapshot):
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md1,580 words
Files3
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈70
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
6,005
on trigger
The instruction body and 2 supporting files, read only when the skill fires.
3.0%
of a 200k window
Ten skills this size would take about 30% of the window before you open a file.
050k100k150k200k context window

6.1k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

3 files, 24.3 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md11.9 kB
  • references/event-sources.md7.1 kB
  • references/powertools-patterns.md5.3 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 3 files you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# You MUST publish a version after enabling SnapStart · 6.1k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/you-must-publish-a-version-after-enabling-snapsta/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/you-must-publish-a-version-after-enabling-snapsta" ] && { [ ! -e .claude/skills/you-must-publish-a-version-after-enabling-snapsta ] || { mv .claude/skills/you-must-publish-a-version-after-enabling-snapsta "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/you-must-publish-a-version-after-enabling-snapsta" .claude/skills/ && echo "Installed .claude/skills/you-must-publish-a-version-after-enabling-snapsta"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add aws-samples/you-must-publish-a-version-after-enabling-snapsta

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/you-must-publish-a-version-after-enabling-snapsta/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/you-must-publish-a-version-after-enabling-snapsta/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/you-must-publish-a-version-after-enabling-snapsta" ] && { [ ! -e ~/.claude/skills/you-must-publish-a-version-after-enabling-snapsta ] || { mv ~/.claude/skills/you-must-publish-a-version-after-enabling-snapsta "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/you-must-publish-a-version-after-enabling-snapsta" ~/.claude/skills/ && echo "Installed ~/.claude/skills/you-must-publish-a-version-after-enabling-snapsta" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/you-must-publish-a-version-after-enabling-snapsta/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as lambda in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, you-must-publish-a-version-after-enabling-snapsta.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referenceaws-samples/you-must-publish-a-version-after-enabling-snapsta

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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