@layervai/qurl-mcp

⚠️ 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.

A qURL MCP Server that supports both local stdio mode and remote HTTP mode for creating, managing, resolving, and sharing secure access links.

Overview

qURL MCP exposes qURL capabilities to MCP clients, GPTs, ChatGPT, and other remote integrations.

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
• serving public legal pages
• serving a configurable MP4 video playback page

Runtime Modes

Feature Map

qURL Management Tools

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. Connector upload and qURL minting are separate operations. 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. 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:

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

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.

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, 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 first. Size the configured maximum and reverse-proxy concurrency limit together.

Set QURL_API_KEY in the environment for stdio mode. 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. 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.

HTTP fields have matching environment overrides:

The listener defaults to 127.0.0.1. A non-loopback host is rejected unless allowedHosts is explicitly configured. Set trustProxyHops (or MCP_TRUST_PROXY_HOPS) to the exact number of trusted proxy hops; leave it at 0 for direct connections so forwarded IP headers cannot spoof rate-limit keys. The Host allowlist is limited to 1,000 entries so request-time validation stays bounded even under pathological operator configuration. /mcp applies the configured request allowance independently to both the client IP and the SHA-256 digest of the authenticated bearer. The memory store is process-local; the DynamoDB store uses an atomic fixed-window counter keyed by credential digest and UTC minute. It never stores the bearer. As with any fixed window, requests around a minute boundary can total nearly twice the configured allowance. The table contract is a string partition key named rate_key; the atomic update writes a numeric request_count counter and a numeric expires_at TTL timestamp. Enable DynamoDB TTL on expires_at so expired rows do not accumulate; TTL only schedules asynchronous cleanup, and the minute in the key—not physical deletion—resets the active window. The task role requires dynamodb:DescribeTable for startup and dynamodb:UpdateItem on the request path. Use on-demand capacity or provision enough write capacity for the expected fleet rate; throttling fails closed with 503 and never falls back to memory. The client uses standard retry mode with at most two attempts, a one-second connection timeout, and a two-second request timeout that throws; these explicit bounds limit how long a request holds a concurrency permit during a partial store failure. The optional AWS SDK dependency is top-level exact-version pinned, while the committed package lock fixes its transitive @aws-sdk/* and @smithy/* graph. Any SDK bump must update the lockfile and keep the real-NodeHttpHandler timeout-materialization regression test green. The dependency is loaded only when the DynamoDB store is selected, so stdio-only consumers may install with --omit=optional. Deployed HTTP images must include optional dependencies; startup fails before listening if the SDK is absent or exposes an incompatible runtime surface. The client uses the standard AWS_REGION and credential provider chain; ECS deployments normally obtain both from the task environment and task role. Reverse-proxy deployments must set the correct hop count or all callers behind the proxy will share the proxy's single IP bucket. Only the DynamoDB credential quota is fleet-wide: the IP limiter is process-local, so its effective fleet allowance multiplies with task count and must be backed by a shared edge limit. The managed deployment in qurl-integrations-infra PR #1305 enforces both a per-source-IP WAF limit and a lower aggregate /mcp fleet cap, with live headroom proof tracked in issue #1306. The credential bucket also prevents one key from bypassing the request allowance by rotating source IPs, while maxSessionsPerCredential prevents it from occupying the full session pool. Each distinct bearer value retains one credential-bucket entry for the current one-minute window. The IP limiter runs first, so token rotation from one source cannot create entries faster than mcpRateLimitPerMinute; hostile distributed traffic still requires the documented shared edge limit. The IP bucket is the primary in-process control against arbitrary bearer rotation because distinct unvalidated bearer strings necessarily occupy distinct credential buckets. In stateful mode, budget pending-session parser memory as maxUnvalidatedSessions times roughly 1.5 times the smaller of maxUploadFileDataBytes and 10 MB (plus about 64 KiB per request). At the defaults, the theoretical concurrent ceiling is about 1.5 GiB. Lower maxUnvalidatedSessions and the shared edge concurrency limit together when the deployment has a smaller memory budget. Bearer credentials are conclusively validated by the first successful downstream qURL API call. Until then, sessions use the smaller pending-session cap and one-minute validation deadline, so arbitrary non-empty bearer strings cannot occupy the full session pool for the normal 15-minute TTL. A client that performs only MCP introspection remains pending by design; after deadline eviction it must re-initialize before its next request. The session caps and validation deadline are configurable for clients with longer introspection-to-tool-call gaps. The deadline is absolute and applies regardless of activity, including an open SSE stream or a long-running first tool call. Validated clients that disconnect without sending DELETE /mcp retain their bounded session slot for a 30-second reconnect grace period. A reconnect clears that deadline; otherwise the session is reaped without waiting for the longer idle TTL. Size maxSessions and the idle TTL for clients that remain connected but do not perform explicit session teardown. Validated sessions also expire at sessionAbsoluteTtlMs (24 hours by default), even during an active SSE stream or tool request. This prevents keepalives from pinning a global or per-credential session slot indefinitely. The first downstream qURL operation must therefore complete before that deadline; an unusually slow first API call may be interrupted and the client must re-initialize. This fail-closed behavior prevents an invalid credential from extending its pending slot with a deliberately long-running request. Accepting a non-empty bearer during MCP initialization is intentional: it keeps protocol introspection available before the first qURL operation, while the global session cap, per-credential session cap, pending-session cap, absolute deadline, and request rate limit bound invalid-key slot usage. The MCP middleware does not validate the key itself; only a successful downstream qURL API response promotes the session. Downstream errors, including non-2xx responses that appear authenticated, do not promote it because an intermediary may have generated them before the qURL API authenticated the bearer. Promotion therefore assumes the configured HTTPS qURL API endpoint and every trusted intermediary neither cache nor synthesize authenticated success responses. Reverse proxies in that path must forward authorization and disable response caching for qURL API traffic. Consequently, any caller with a non-empty bearer can enumerate the public tool/resource/prompt catalog and briefly hold bounded pending-session state. On hostile networks, place non-loopback deployments behind an identity-aware proxy that preserves the caller's qURL bearer credential for /mcp authorization. Initialization and catalog listing return server-owned static metadata only; they do not invoke tool/resource/prompt handlers, read host files, contact the qURL API or connector, or send email. Handler calls rely on the configured qURL API to authenticate the forwarded bearer before returning data or applying an operation. The configured connector is a second credential authority: it must authenticate the forwarded qURL bearer before accepting or storing upload bytes. Deploying an unauthenticated connector is unsupported because it would allow an unvalidated MCP caller to create connector-side state.

Stateful mode is the compatibility default and retains the existing MCP session registry, GET SSE, explicit DELETE behavior, and process-local credential quota charging for all three MCP methods. Stateless mode creates and closes a server and transport for each POST, ignores mcp-session-id, and returns JSON-RPC-shaped 405 responses for GET and DELETE. It is the required mode behind a load balancer or autoscaling service because no request depends on process-local affinity. The concurrency permit is acquired before JSON parsing and released on every response/error/disconnect path. Stateless mode uses the configured maxUploadFileDataBytes parser ceiling directly because the pre-parse concurrency permit provides its memory-amplification bound. Budget roughly maxConcurrentRequests times (1.5 times maxUploadFileDataBytes plus 64 KiB) per process; the default concurrency at the 100 MB upload ceiling is approximately 3 GiB before downstream work. Stateless startup rejects configurations whose conservative parser budget exceeds 4 GiB. Lower either setting further when the ECS task has a smaller memory limit. In contrast, stateful sessions above the default ceiling must first complete a successful downstream qURL API call. On hostile networks, an authenticated edge request-size limit no larger than the configured parser ceiling is a deployment requirement: the permit bounds aggregate memory, but a non-empty bearer is not authoritatively validated until the parsed operation reaches the downstream qURL API.

The stateless listener bounds header receipt at 15 seconds and both complete request receipt and idle socket lifetime at 120 seconds. A concurrency permit spans parsing through response completion, so stalled clients cannot retain the entire permit pool indefinitely. A tool call that produces no socket traffic for 120 seconds is intentionally aborted; integrations needing longer silent operations must move that work behind an asynchronous API rather than raising this fleet-wide retention bound.

Deployed (non-loopback) stateless mode requires the DynamoDB credential store and all three stable metric identity fields. It emits a 30-second EMF heartbeat: McpConcurrencyUtilization is the peak permit utilization observed during the interval at request admission and heartbeat (including requests that start and finish between heartbeats), while McpConcurrencyRejected and McpRateLimitStoreErrors are snapshot-and-zero interval deltas that include explicit zeros. Session caps and email recipient quotas remain in-memory; the DynamoDB credential quota is fleet-wide and counts every authenticated HTTP POST, including initialization, discovery, and tool calls. Size that quota for the expected complete request pattern rather than tool calls alone. The permit also spans the bounded DynamoDB increment: during a store brownout, each admitted request may retain one permit for roughly four seconds (two two-second attempts) before failing closed, while excess requests receive a fast concurrency 503. The fixed-window counter increments every attempt, including attempts already above the credential limit; edge rate limits and DynamoDB write/throttle alarms must therefore bound abusive write amplification. Deployment owners must make both alarms and an over-limit write-amplification probe hard promotion gates rather than treating them as optional observability. The managed deployment in qurl-integrations-infra#1305 provisions those alarms, with live proof tracked in its rollout ledger and issue #1306 before promotion. Direct createHttpRuntime embedders that inject a credential-store implementation must still declare credentialRateLimitStore: "dynamodb" for non-loopback stateless mode. The generic injection interface cannot prove a custom backend is shared across replicas, so injection is deliberately not an escape hatch from the deployed contract. Metric identity fields are rejected in stateful mode so the concurrency gauge cannot silently report a misleading zero. Each stateless POST owns a fresh MCP server and transport so no request can inherit another credential's handler state. Completed-response teardown is tracked asynchronously. Admission stops when that backlog reaches maxConcurrentRequests; requests already in flight may then finish, so the backlog can transiently approach twice that count but remains bounded. While the admission guard is closed, new requests fail with 503 and increment McpConcurrencyRejected instead of growing teardown memory without bound. That counter intentionally represents admission failure from either active request saturation or teardown backpressure. Autoscaling must use McpConcurrencyUtilization alone; the rejection counter remains page-worthy, and low utilization alongside rejections identifies teardown lag. Pooling these objects would weaken request isolation and is deliberately not a performance optimization without measured registration pressure. /healthz and the public video-file endpoint each use their own publicFileRateLimitPerMinute bucket, isolated from legal/video-page traffic and from each other. Keep load-balancer, liveness-probe, and expected video range-request frequency below that per-source-IP allowance (300 requests/minute by default), or raise it for unusually aggressive clients.

Configuration Priority

By default, configuration is loaded from the two local JSON files above. If a file is absent, built-in defaults and environment variables are used. Relative config paths—including the defaults—are resolved from the process working directory. Set the explicit path variables below when a supervisor, npx, or an MCP host launches the server from a different directory.

The following environment variables independently override the config file paths:

• QURL_MCP_CONFIG
• QURL_MCP_HTTP_CONFIG

QURL_MCP_HTTP_CONFIG never replaces the shared runtime config path. This keeps listener settings from silently shadowing SMTP, connector, or API settings.

server.json and smithery.yaml describe the published stdio transport, so they include shared upload/SMTP settings but intentionally omit HTTP-only listener variables such as QURL_MCP_HTTP_CONFIG and MCP_MAX_SESSIONS.

Do not commit API keys, SMTP credentials, or private file-system paths.

HTTP Routes

After starting in http mode, the common routes are:

/healthz is intentionally unauthenticated and Host-unvalidated for every caller, exposes only { "ok": true }, and uses the configured public-route request limit in a separate bucket so health probes cannot consume the legal/video route allowance. A 429 from this route means the probe source exceeded publicFileRateLimitPerMinute, not that the application failed its liveness check; keep probe frequency below that limit. It is registered before Host validation because ALB target probes use the task IP and port as Host; public MCP and browser routes remain Host-validated.

HTTP Authentication

The /mcp endpoint requires Authorization: Bearer <qURL API key> on every request. In stateful mode the bearer token is bound to the resulting MCP session, so a session ID cannot be reused with a different credential. In stateless mode the bearer remains request-scoped and is discarded when the response closes.

Operator authentication boundary: initialization accepts any non-empty bearer token and allows the public tools/resources/prompts catalog to be read before authoritative validation by the first downstream qURL API call. That catalog is assembled from static schemas and descriptions and does not include bearer tokens, SMTP credentials, or other operator configuration. Unvalidated-session caps, a short validation deadline, and request rate limits bound that pre-validation state; the supplied token is forwarded only to the configured qURL API. Introspection-only sessions therefore remain unvalidated and are closed at unvalidatedSessionTtlMs; clients can re-initialize if they need a longer-lived session. A session is promoted only after a successful qURL API call—rejected or rate-limited calls do not prove the credential valid. Disconnected sessions remain registered for a 30-second SSE reconnect grace period, while maxSessions and maxSessionsPerCredential bound that allowance under churn.

Requests without an Origin header are accepted for non-browser MCP clients. When Origin is present, it must match the origin of baseUrl; malformed or cross-origin values are rejected on /mcp. Public health, legal, and configured video routes do not use browser-origin state and are not gated by this check.

Configure remote MCP clients with:

If a client only supports OAuth discovery, place an OAuth-compatible gateway in front of this server rather than exposing /mcp without authentication.

How to Verify Deployment

Service-Level Checks

Start with:

• /healthz
• /mcp

Public Page Checks

Also verify the legal pages and, when configured, the video page:

• /legal/privacy
• /legal/terms
• the configured public video page path

Domain Verification

If you plan to use OpenAI Platform, make sure the following root-level path exists:

/.well-known/openai-apps-challenge

This verification file must live under the domain root .well-known path, not under /mcp.

Docker

The repository includes a Dockerfile for containerized deployment.

Example:

docker build -t qurl-mcp .
docker run -i -e QURL_API_KEY=lv_live_xxx qurl-mcp

If you deploy with Docker, make sure the container can still access the correct config files, or override the config file paths with environment variables.

Run HTTP mode locally in Docker:

The image defaults to the stdio entry point and the HTTP server defaults to container-local loopback. HTTP deployments must override the command and bind to 0.0.0.0 with an explicit Host allowlist:

docker run --rm -p 3000:3000 \
  -e MCP_HOST=0.0.0.0 \
  -e MCP_ALLOWED_HOSTS=127.0.0.1,localhost \
  qurl-mcp node dist/http.js

For a single trusted production reverse proxy, set MCP_TRUST_PROXY_HOPS=1, use the public HTTPS origin in MCP_BASE_URL, and set MCP_ALLOWED_HOSTS to the public hostname. Do not expose the container's listener directly when proxy trust is enabled.

Common Commands

Recommended Deployment Order

1. Copy and update the two example config files
2. Set credentials through environment variables
3. Run npm install
4. Run npm run build
5. Run npm run start:http
6. Verify /healthz
7. Verify unauthenticated /mcp requests receive 401
8. Configure the HTTPS reverse proxy
9. Verify an authenticated MCP initialization and the optional public pages

Third-Party Assets

Text-to-PDF generation bundles the 17.8 MB Noto Sans SC variable font for offline multilingual glyph coverage. This intentionally increases the npm tarball to roughly 11.4 MB and the unpacked package to roughly 18.4 MB for all installs, including deployments that do not enable PDF workflows. Shipping the font in-package avoids a runtime network dependency and preserves predictable CJK rendering; operators prioritizing a smaller install can remove the asset and accept the documented Helvetica fallback with limited CJK coverage. Its SIL Open Font License and copyright notice are included in assets/fonts/OFL.txt.

License

MIT -- LayerV AI