Portless - Named .localhost URLs Agent Skill

Replace port numbers with stable named .localhost URLs for local development.

Context cost
5.3k tokensestimated from the bundle, loaded when it triggers
Bundle
1 file · 21.0 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Replace port numbers with stable named .localhost URLs for local development

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.

developer tools

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.md21.0 kB · preview
--- name: portless-local license: MIT compatibility: cline, claude, opencode, amp, codex, gemini, cursor, pi hint: Use when you want clean, named URLs for local development instead of remembering port numbers user-invocable: true disable-model-invocation: true metadata: audience: all workflow: development source: vercel-labs/portless@7abf4df5d939fe3b527a120e20bc270c681c3536 source_path: skills/portless/SKILL.md ---
16# Portless - Named .localhost URLs
17
18Replace port numbers with stable, named .localhost URLs for local development. For humans and agents.
19
20> **Note:** The portless CLI enables HTTPS on port 443 by default (https://myapp.localhost). Pass --no-tls to portless proxy start, or set PORTLESS_HTTPS=0, for plain HTTP. Keep HTTPS when the app needs OAuth, secure cookies, or HTTP/2.
21
22## Safety and Approval
23
24Read existing proxy configuration before starting an app: auto-start reuses saved settings, including LAN mode. Outside LAN mode the proxy binds only to IPv4/IPv6 loopback; LAN mode binds all interfaces.
25
26Ask for explicit approval before first-run sudo/elevation, CA trust-store changes, /etc/hosts writes, LAN exposure, Tailscale sharing, public Funnel/ngrok tunnels, startup-service installation/removal, or destructive cleanup. A request for local development does not authorize these actions. Use PORTLESS_SYNC_HOSTS=0 when hosts writes are not approved. In non-interactive environments, first-run prompts fail rather than granting permission; pre-start only an approved proxy configuration.
27
28--force kills the existing process and takes over its route. prune terminates orphaned process groups, and prune --force uses SIGKILL. Do not use them without checking ownership and approval. clean also removes startup services and trust entries; it is not routine project cleanup.
29
30Never print or commit TLS private keys or ngrok tokens. Let the user configure authentication through the provider's private credential workflow. Do not disable TLS verification to resolve proxy errors.
31
32## Why Portless?
33
34Local dev with port numbers is fragile. Portless fixes that by giving each dev server a stable, named .localhost URL.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md2,768 words
Files1
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.

≈130
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
5,120
on trigger
The instruction body, read only when the skill fires.
2.6%
of a 200k window
Ten skills this size would take about 26% of the window before you open a file.
050k100k150k200k context window

5.3k 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

1 file, 21.0 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md21.0 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file 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.

# Portless - Named .localhost URLs · 5.3k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/portless-named-localhost-urls/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/portless-named-localhost-urls" ] && { [ ! -e .claude/skills/portless-named-localhost-urls ] || { mv .claude/skills/portless-named-localhost-urls "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/portless-named-localhost-urls" .claude/skills/ && echo "Installed .claude/skills/portless-named-localhost-urls"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add jellydn/portless-named-localhost-urls

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/portless-named-localhost-urls/ 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/portless-named-localhost-urls/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/portless-named-localhost-urls" ] && { [ ! -e ~/.claude/skills/portless-named-localhost-urls ] || { mv ~/.claude/skills/portless-named-localhost-urls "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/portless-named-localhost-urls" ~/.claude/skills/ && echo "Installed ~/.claude/skills/portless-named-localhost-urls" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/portless-named-localhost-urls/ 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 portless-local in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, portless-named-localhost-urls.

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
Referencejellydn/portless-named-localhost-urls

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.

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