Qurl MCP Server

qURL MCP server for temporary access links

Give an AI agent tools to share localhost web apps, private APIs, and selected files through expiring qURL™ by LayerV access links. This repository implements the Model Context Protocol server for that workflow. The @layervai/qurl-mcp package runs as a local stdio server backed by the qURL CLI or API, or as an authenticated remote HTTP server backed by the API.

Start with the no-account local quickstart or account-backed client configuration, then choose the tools for your task. In local mode, publish_crid runs the installed CLI to publish an app that is already running; share_by_crid issues its access link. Creating a link alone does not publish an app or restrict an existing public URL. Uploads require the account-backed tool set and use a separate connector lifecycle; see upload tools for their supported options and limits.

Local app sharing · File sharing · Sharing questions · Private links

⚠️ Renamed from @layerv/qurl-mcp in v0.4.0. The old package is deprecated and will not receive further updates. If you're using @layerv/qurl-mcp@0.3.x, swap the scope in your MCP client config — same binary, same API key, no other changes.

Let an AI agent share a localhost preview

Use this workflow when an agent needs to give a reviewer access to a development preview or internal API. A tool that creates a link does not start the app on your laptop.

1. Keep the local app running. Configure a local stdio MCP client using the no-account quickstart, with the qURL CLI installed on the same host and no QURL_API_KEY set.

2. Ask the agent to call publish_crid with app_name (a short public name, without secrets or recipient details) and the app's root loopback URL, such as http://127.0.0.1:3000, and save the returned CRID. Alternatively, publish it directly with the CLI. Local tools use that machine's device identity; a CRID does not grant another device authority over the resource.

3. Ask the agent to call share_by_crid with the published CRID and a requested lifetime. The following is a tool argument object, not a complete MCP message:

   {
     "crid": "REPLACE_WITH_PUBLISHED_CRID",
     "ttl": "5m"
   }
   

4. Share the full returned link through your intended private channel and report the expiry returned by the service. Do not assume the requested TTL was granted unchanged. Keep the publishing host and app available.

Check that your installed release exposes these tools. In account-backed mode, share_by_crid instead uses the API credential and requires qurl:resolve and resource authorization. For resources already managed through the API, see mint_link and the other link-management tools. Tool availability and resource identifiers matter; an uploaded-file identifier cannot be substituted into the same workflow.

Let an AI agent share a PDF or image

For example, give a reviewer a short-lived link to a selected PDF report. Use account-backed stdio mode (QURL_API_KEY set) or authenticated HTTP mode, then configure the upload Connector under configuration files. Upload tools are not listed in no-account local mode. Choose the tool for the transport:

A stdio tool argument example:

{
  "file_path": "/absolute/path/to/review.pdf",
  "expires_in": "5m",
  "one_time_use": true
}

Pass these arguments to upload_file_qurl only for a file the user selected. The tool uploads to the configured file service and returns a new access link. Use the confirmed expiry in its response. Opening a single-use link to test it can consume it before the recipient opens it.

Upload links cannot currently be revoked through this MCP server, and mint_link cannot create another link for an uploaded file. See upload tools for the supported formats, size limits, response fields, and cleanup limitations.

Choosing what an agent should share

Should the agent share an app or a deployed preview?

If the reviewer needs the current localhost app, keep it running and use the local CLI-backed tools to publish the resource and issue its link. An existing ngrok endpoint, Cloudflare application, or Vercel preview is another possible handoff, but its access controls and availability come from that separately configured service. This server exposes qURL operations; it does not create those other deployments. See the app-sharing comparison when choosing the workflow. Share the confirmed expiry and preserve the app's login requirements.

Should the agent upload the result or link to a running file service?

A selected PDF or image can use this server's account-backed upload tools. A hosted Google Drive document instead uses Drive's sharing permissions; an S3 object can use a presigned download URL. Those storage workflows are distinct from publishing a local file server, which must remain available. Choose based on where the result should live and which service the agent is authorized to use. This server's upload identifiers and revocation limits still apply; a file path, uploaded-file identifier, and local-service CRID are not interchangeable.

MCP sharing questions

Is this a public tunnel to my localhost app?

In no-account stdio mode, this server invokes the local CLI to publish and manage an already running app. API-backed and remote HTTP modes use their configured resources; a remote server cannot publish an app on your laptop through its own localhost address. Use the localhost-sharing comparison when choosing between resource access links and a public endpoint workflow.

Does every AI client support the same tools?

No. Configure the client's supported transport and check the installed server's tool list. A remote HTTP server cannot use upload_file_qurl to read a file from the client's laptop; use the file-data tool for a supported attachment.

Can I use an app link and an uploaded-file link interchangeably?

No. App resource management and uploaded-file link minting use different lifecycles. Follow the tool that issued the link, including its revocation limits. Your local app's own login continues to apply when the link opens it.

Overview

The server exposes qURL operations as MCP tools for clients that support the configured transport. See the LayerV MCP guide for product setup and the tables below for the capabilities in this source version.

It currently supports:

• creating, reading, updating, and deleting qURLs
• resolving access tokens
• managing qURL tokens and sessions
• uploading text or file content and generating qURLs
• optionally serving LayerV public legal pages
• serving a configurable MP4 video playback page

Quick start: no account needed

Share an app running on your machine, or a URL, privately from Claude Desktop, Claude Code, Cursor, Codex, or any local MCP client. You need no account and no API key: with no QURL_API_KEY set, the server drives the qURL CLI installed on your machine, and the first publish creates this machine's identity by itself.

1. Install the qURL CLI (macOS and Linux; Node.js 22.12 or later is needed for the MCP server):

(umask 022 && mkdir -p "$HOME/.local/bin" "$HOME/.local/state") && chmod go-w "$HOME/.local" "$HOME/.local/bin" "$HOME/.local/state" && curl -fsSL --proto '=https' https://raw.githubusercontent.com/layervai/qurl-integrations/main/scripts/install.sh | INSTALL_DIR="$HOME/.local/bin" sh

On Windows, download qurl.exe from the latest release and put its folder on PATH. The server finds qurl on PATH, and also in ~/.local/bin, /opt/homebrew/bin, and /usr/local/bin, which many MCP clients leave off the PATH they give servers. If the CLI is missing, every tool answers with this install command instead of failing.

2. Add the server to your MCP client, with no env block.

Claude Desktop (claude_desktop_config.json) and Cursor (~/.cursor/mcp.json):

{
  "mcpServers": {
    "qurl": {
      "command": "npx",
      "args": ["-y", "@layervai/qurl-mcp"]
    }
  }
}

Codex (~/.codex/config.toml):

[mcp_servers.qurl]
command = "npx"
args = ["-y", "@layervai/qurl-mcp"]

Claude Code:

claude mcp add qurl -- npx -y @layervai/qurl-mcp

3. Ask for what you want, for example "share the app on localhost:3000 with my client". The agent publishes the app (it stays on your machine; the CLI's background service keeps the share running), and gives you a short-lived link for one person, or turns on access requests so people can ask for access.

Tools without an account

The tools follow the same rules as the qURL agent skill (https://layerv.ai/skills/qurl/SKILL.md):

• Everything is published private. These tools have no option to publish publicly.
• A pending access request is approved only with the six-digit code the person gives you. No listing shows a code, and no tool approves by name: anyone can type any name, and names come back as unverified data.
• An access link is a bearer secret for one recipient. A CRID grants nothing by itself and is safe to share.

The server runs the CLI with an argument array (never a shell), with JSON output, closed stdin, a timeout, and bounded output, and it does not log what the CLI prints. The tools that need an account key (the qURL link, token, session, and upload tools, and the qurl:// resources and prompts) are not listed in this mode.

With an account key

Set QURL_API_KEY to a LayerV API key and the server uses the qURL API directly, with the full tool set described in the feature map:

{
  "mcpServers": {
    "qurl": {
      "command": "npx",
      "args": ["-y", "@layervai/qurl-mcp"],
      "env": { "QURL_API_KEY": "lv_live_xxx" }
    }
  }
}

Remote HTTP server

The HTTP transport (qurl-mcp-http) serves remote agent runtimes. It is account-based: every request carries the caller's qURL API key as a bearer token, and it never runs a local CLI. See HTTP Authentication and the LayerV MCP guide.

Private consumer access

Node.js 22.12 or later is required by the shared qURL SDK.

publish_crid creates a private URL resource with keys, invite_only, email_capture, review, or contract access. manage_crid_access changes the policy with its current version, sends invitations, lists grants, approves or denies requests, and removes access. The tools return resource-scoped receipts and omit invitation secrets and bearer links. Local apps use the qURL CLI on the publisher machine. In local mode, app_name is required and sets and confirms the public preview name through qurl preview set (requires a CLI with that command). If naming fails, the tool returns an error with the published CRID and recovery instructions. It does not delete or republish the resource. Callers must now provide app_name; use the user's app name or a short neutral name without secrets or recipient details. Include the returned name and browser address in the answer even when invitation emails are sent.

For example, an assistant can turn “share this with ana@example.com, and allow no requests” into an invite_only resource and an authorized invitation. For email capture, the consumer must know that the publisher receives their verified email. A verified email proves mailbox control, not legal identity. Contract approval requires a trusted publisher backend entitlement receipt; these tools do not verify payment. Do not report connection removal as complete while session_cleanup is pending.

This feature requires the matching service and admission readers. Keep it disabled until the publisher and consumer journeys pass. The package pins the published SDK 3.0.0 and supports clean installation with dependency scripts blocked. This release requires Node.js 22.12 or later; Node.js 20 is no longer supported.

Runtime Modes

Feature Map

qURL Management Tools

share_by_crid recognizes a standalone $<CRID> value as an explicit request to mint a temporary link for that CRID. The $ is a user-facing marker and is removed before the CRID is sent to the qURL API. A bare CRID remains supported. This tool requires qurl:resolve. Its optional Go-duration ttl must resolve to a positive whole number of seconds. The service clamps the requested lifetime. Sharing makes one request with a 30-second timeout and does not automatically retry. Repeating the tool call can mint another link.

Resource status filters accept active, revoked, or active,revoked. A resource remains active or revoked even when its expires_at is in the past; individual access tokens can expire. expired is not accepted by list_qurls, even though response parsing tolerates legacy values. The snapshot retains upstream's stale expiration prose; its active/revoked status enum is authoritative.

The qURL SDK reuses the same Idempotency-Key and request body when retrying POST/PATCH requests after a network failure or HTTP 429. Mutating HTTP 5xx responses are not automatically retried. Each new MCP tool invocation is a new operation with a new key, so repeating create_qurl, batch_create_qurls, or mint_link can mint additional tokens. MCP does not expose a caller-supplied key.

Upload Tools

upload_file_qurl is intentionally stdio-only. It can read any supported PDF/image that the local MCP process user can access, so agents should invoke it only for a path the user explicitly selected for sharing. Do not expose it to untrusted prompts or autonomous agents: prompt injection could otherwise select another readable PDF/image on the host. Run stdio under an OS account whose filesystem access is limited to intended shareable content. HTTP mode never registers this host-file tool. The byte/text tools are also available in stdio so local clients can share in-chat attachments without first materializing them at a known host path. To recover after a successful upload but a failed mint, keep the returned resource_id and call mint_uploaded_file_link. This makes one mint attempt without uploading the file again. Each call can create a new live link. A timed-out or failed prior mint may already have created one, so reconcile that result before retrying automatically. Existing links are not cancelled. The response contains the new link and its expiry status.

Connector upload and link minting are separate operations. The link comes from the connector's POST /api/mint_link/:resource_id (in tunnel mode, a per-recipient watermarked view), not from qURL mint_link, so uploaded files cannot be re-linked with mint_link. Use mint_uploaded_file_link with the saved resource_id instead. Upload links support expires_in (1m-30d, converted to an absolute expiry on the MCP host's clock, so a host clock that is off shortens or lengthens the link; a link whose returned expiry is already past by this host's clock is returned with expires_at_already_past), one_time_use, and session_duration (whole seconds, up to 24h); access_policy and max_sessions must be omitted or null; non-null values are rejected before the upload. If the connector ever mints more links than requested, the result reports how many extra in unexpected_extra_link_count and any IDs it returned in unexpected_extra_qurl_ids (at most 10); they may be live even when this host's clock suggests expiry, so tell the user. If minting fails after upload, the connector currently has no delete endpoint; the server logs the orphaned resource_id for operator cleanup and returns the mint failure. Upload links cannot yet be revoked from this server: delete_qurl on the upload's resource_id does not stop a connector-minted link (revocation needs the connector's /api/revoke_links), so prefer short expiries for sensitive files. Duration inputs accept whole days or weeks (7d, 1w), or unsigned Go-unit sequences (1h30m, 1.5h). Mixed day/week sequences (1d12h), leading signs, leading-dot fractions, and Greek mu (μs) are rejected; micro sign (µs) is accepted. HTTP upload attempts remain bounded by the per-IP and per-credential MCP rate limits; stdio operators should separately constrain autonomous retry loops. Upload validation binds the declared media type to the filename plus format start/end markers; it is not a malware scanner or full PDF/image decoder. For polyglot resistance, a PDF's final %%EOF marker must be followed only by ASCII whitespace; producer output with other trailing bytes is rejected even if a permissive PDF reader would accept it. JPEG validation checks framing and terminal markers rather than decoding image segments. The authenticated connector must independently decode or otherwise fully validate content before storage when semantic media validity matters. It must also preserve the declared safe media type and serve downloads with X-Content-Type-Options: nosniff rather than inferring an executable type. There is intentionally no application-level path allowlist: symlinks and time-of-check/time-of-use races make a lexical prefix check a misleading security boundary. Use a dedicated OS account, container, or read-only mount whose readable files are already limited to the intended sharing directory. The final path component is opened with O_NOFOLLOW; intermediate directory symlinks retain normal filesystem behavior under this trusted-local-user boundary.

MCP Resources

MCP Prompts

Quick Start

1. Install Dependencies

npm install

For a local stdio-only source install, use npm install --omit=optional; this omits the AWS SDK. HTTP deployments using the DynamoDB credential quota must use the ordinary install so the optional SDK is packaged.

2. Build

npm run build

3. Start

Local stdio mode:

npm run start

Remote HTTP mode:

npm run start:http

MCP Client Example

If you want to use this server in stdio mode with a local MCP client, use the configuration from Quick start. Leave out env to work without an account through the local qURL CLI, or add "env": { "QURL_API_KEY": "lv_live_xxx" } to use the qURL API with an account key.

Configuration Files

Copy the tracked examples to create local configuration files:

cp qurl-mcp.config.example.json qurl-mcp.config.json
cp qurl-mcp.http.example.json qurl-mcp.http.json

The local files are gitignored so credentials and machine-specific paths are not committed.

Their responsibilities are:

qurl-mcp.config.json Reference

Shared Core Settings

Shared settings have these environment overrides. Environment values take precedence over the shared config file. The process caches resolved shared settings but automatically invalidates that cache when the file metadata or any relevant environment value changes.

Set QURL_LINK_HOSTS=qurl.link,files.example.com (or linkHosts as a JSON array) to restrict connector-minted upload links before they are returned or emailed. Entries are exact ASCII hostnames or IPs, without schemes, ports, paths, or wildcards. Subdomains need their own entries. The policy checks the hostname; existing HTTPS and loopback development rules still apply. When neither source has a non-empty list, custom-domain behavior stays unchanged. A blank environment list falls back to any file policy; clear the file list to disable that policy. The tracked example config uses an empty list. Configure all legitimate link hosts before enabling it. A rejected mint may already have created a live link and stored file; the error reports that state and does not retry the upload.

QURL_API_KEY is intentionally environment-only and has no config-file field. Prefer QURL_SMTP_PASSWORD for the SMTP secret as well. If smtp.password is stored in the config file on a POSIX host, restrict that file to owner-only permissions (for example, chmod 600); startup warns when group/other read bits are present. This check is intentionally advisory so existing deployments do not fail after an upgrade, and it is skipped on Windows because POSIX mode bits are not available there. Email delivery itself is fail-closed unless at least one exact smtp.allowedRecipients entry or smtp.allowedRecipientDomains entry is configured; startup warns when complete SMTP credentials lack that policy.

Raising maxUploadFileDataBytes also raises the HTTP JSON parser's per-request memory ceiling to roughly 1.5 times that value (up to about 150 MB at the 100 MB maximum), before base64 decoding applies the exact byte cap. Until a session has completed a successful downstream qURL API call (a completed upload's link mint counts), its parser ceiling remains at the smaller 10 MB default upload setting; clients configured for a larger first upload must validate the session with a small qURL API call or a smaller upload first. Size the configured maximum and reverse-proxy concurrency limit together.

Set QURL_API_KEY in the environment for stdio mode to use the qURL API. Without it, stdio mode runs through the local qURL CLI and needs no account (see Quick start). In HTTP mode, every client request supplies its own qURL API key as a bearer token.

defaultQurlApiUrl and QURL_API_URL require HTTPS for non-loopback hosts because qURL API keys and data are bearer-sent to that destination. Plain HTTP is accepted only for literal loopback development endpoints. Upload connector URLs follow the same HTTPS-except-loopback rule. Loopback means 127.0.0.0/8 or ::1; wildcard bind addresses such as 0.0.0.0 and :: are intentionally not accepted as outbound HTTP targets. Connector destinations are trusted operator configuration rather than caller input; private addresses and DNS resolution are therefore permitted. Pin the connector hostname in deployment DNS and do not point it at metadata services. The caller's qURL bearer credential is forwarded to this host, so treat connector URL and DNS control as part of the credential trust boundary. Configure the connector service base URL, not an upload route: qurl-mcp appends /api/upload to ordinary base paths, accepts that exact endpoint suffix, and rejects ambiguous upload-like paths such as /upload or /api/upload/v2. The MCP server performs bounded file-framing checks, not full media parsing; the connector must independently revalidate uploaded content before storage or serving, and delivery must retain nosniff behavior as the authoritative type boundary.

API and connector base URLs that contain embedded credentials, a query string, or a fragment are now rejected during startup. Deployments that previously used one of those unusual URL forms must move credentials to QURL_API_KEY and keep the configured service URL to its origin and optional path prefix.

SMTP Settings

These settings are used when email delivery is requested by tools such as:

• create_qurl
• mint_link
• upload_text_qurl
• upload_file_qurl
• upload_file_data_qurl

If either recipient allowlist is configured, only an exact address or domain match is delivered. If both are empty, the message and hourly caps still apply. Domain entries are exact: example.com does not implicitly allow mail.example.com; list each permitted subdomain explicitly. Addresses and domains are normalized to lowercase NFC/IDNA ASCII form and a trailing DNS root dot is removed before comparison and delivery. Each recipient allowlist is limited to 1,000 configured entries. The per-message recipient cap applies to the complete unique requested fan-out before allowlist filtering, so blocked addresses cannot be used to submit an oversized batch. In HTTP mode, any caller with a valid qURL API key can request a server-side SMTP delivery. Configure allowedRecipients or allowedRecipientDomains before enabling SMTP on an Internet-facing HTTP deployment; empty allowlists permit delivery to any syntactically valid address subject to the quotas. The SMTP transport uses bounded connection/socket timeouts and is closed after each delivery batch. Failed SMTP attempts still consume quota—including when a transient outage results in zero delivered messages—so repeated failures cannot bypass the abuse limit. Each delivery request also has a 60-second aggregate deadline. Recipients not started before that deadline are reported as skipped; provider-side queues are the supported path for larger or slower fan-out. Transport encryption is mandatory: smtp.secure: true uses implicit TLS, while smtp.secure: false requires a successful STARTTLS upgrade. Port 465 is reserved for implicit TLS and therefore requires smtp.secure: true. Hourly quota state is maintained per server process: it resets on restart and is not shared across replicas. Operators running multiple instances should enforce a corresponding aggregate limit at the SMTP provider or gateway. The in-process quota is therefore an abuse backstop, not a durable global safety boundary; restart/scale-out fail-open behavior must be covered by that provider-side limit. Tracking fails closed for new principals after 10,000 principals are retained in one process; existing principals continue to use their current buckets until expired entries are pruned. Restrict qURL API-key issuance and monitor new-principal quota-cap rejections: cycling many valid keys can deliberately hold that shared table at capacity for up to one quota window. The quota uses a fixed one-hour window that starts with the first attempted delivery after the prior window expires. As with any fixed window, traffic immediately before and after a boundary can total nearly twice the configured hourly value; use a provider-side sliding or rolling limit when that boundary burst must be prevented across replicas.

HTTP SMTP delivery is restricted to the operator credential configured in QURL_API_KEY. A different customer's valid qURL key does not authorize use of the operator's SMTP account. Without that explicit operator key, HTTP email delivery is disabled. Stdio retains its local operator trust model. Recipient allowlists and quotas apply in both modes.

Generated qURL links are included in the plain-text email body. Restrict recipients with the SMTP allowlists and configure transport encryption at the SMTP server/provider when link confidentiality matters.

Prefer environment variables for SMTP credentials and policy: QURL_SMTP_USERNAME, QURL_SMTP_PASSWORD, QURL_SMTP_FROM_EMAIL, QURL_SMTP_ALLOWED_RECIPIENTS, QURL_SMTP_ALLOWED_RECIPIENT_DOMAINS, QURL_SMTP_MAX_RECIPIENTS_PER_MESSAGE, and QURL_SMTP_MAX_RECIPIENTS_PER_HOUR.

Public Video Page Settings

When configured, the HTTP server additionally exposes:

• a public video playback page
• a streaming endpoint for the MP4 file

publicVideo.filePath is trusted operator configuration. The final component must be a non-symlink regular .mp4 file; intermediate directory symlinks keep normal filesystem resolution and must therefore remain under operator control. Startup probes this optional asset and warns when it is missing, empty, or not regular, but intentionally keeps the MCP service and /healthz available. The video-file route still fails closed with 404 until the asset is corrected.

qurl-mcp.http.json Reference

Use qurl-mcp.http.example.json for local, stateful development. qurl-mcp.http.stateless.example.json shows every store and metric field required by a deployed stateless service.

Documentation truncated — see the full README on GitHub.