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PromptFax

REMOTE · PROMPTFAX.APP · SCANNED SEP 20

Send a one-off fax from inside ChatGPT or Claude. Pay-per-use, $2-$4.50 per delivered fax.

Available components

remote · promptfax.app 90
0 this week 90 Trust /100
Trust breakdown (7 categories)

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score → Why this is hard to score →

Endpoint Security91
  • The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
  • Authorisation is enforced on tool calls, advertised via RFC 9728 protected-resource metadata. Discovery is public, which costs nothing: no tool can be invoked without a token. View diagnostics → Pass
  • HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
  • HSTS check failed: the Strict-Transport-Security header is absent. See how to fix → View diagnostics → Fail
  • DNSSEC is configured correctly; the domain's records validate against the full chain to the root. View diagnostics → Pass
  • The authorisation server offers only Dynamic Client Registration (RFC 7591), which MCP 2026-07-28 deprecated in favour of Client ID Metadata Documents. View diagnostics → Partial
Transport & Reachability100
Schema Quality & AI Usability67
  • AI-judged instruction clarity (excellent).Pass
  • Context-footprint check failed: tool/resource definitions use about 1405 tokens (~175/item across 8 items; 8 tools + 0 resources), over budget; trim descriptions and params. See how to fix → Fail
  • Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management100
  • No destabilizing schema changes in the last 30 days.Pass
Tool Coverage100
  • 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
  • 100% of tool parameters carry a description.Pass
  • Structured output schemas are declared (100% of tools); any adoption earns full credit.Pass
Tool Safety100
  • No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
  • All 1 tool(s) whose name or description implies an irreversible operation declare an MCP destructiveHint annotation.Pass
  • An AI judge read all 8 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
  • Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.Pass
Install

How do I install the PromptFax MCP server?

PromptFax is a hosted endpoint at https://promptfax.app/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

remote · promptfax.app

# add to Claude Code
claude mcp add --transport http app-promptfax-promptfax 'https://promptfax.app/mcp'
// .cursor/mcp.json
{
  "mcpServers": {
    "app-promptfax-promptfax": {
      "url": "https://promptfax.app/mcp"
    }
  }
}
// .vscode/mcp.json
{
  "servers": {
    "app-promptfax-promptfax": {
      "type": "http",
      "url": "https://promptfax.app/mcp"
    }
  }
}
# ~/.codex/config.toml
[mcp_servers.app-promptfax-promptfax]
url = "https://promptfax.app/mcp"
// opencode.json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "app-promptfax-promptfax": {
      "type": "remote",
      "url": "https://promptfax.app/mcp",
      "enabled": true
    }
  }
}
# add to OpenClaw
openclaw mcp add app-promptfax-promptfax --url 'https://promptfax.app/mcp' --transport streamable-http
# ~/.hermes/config.yaml
mcp_servers:
  app-promptfax-promptfax:
    url: "https://promptfax.app/mcp"
// ~/.netclaw/config/netclaw.json
{
  "McpServers": {
    "app-promptfax-promptfax": {
      "Transport": "http",
      "Url": "https://promptfax.app/mcp"
    }
  }
}
# add to Vellum
assistant mcp add app-promptfax-promptfax -t streamable-http -u 'https://promptfax.app/mcp'
// mcp.json
{
  "mcpServers": {
    "app-promptfax-promptfax": {
      "type": "http",
      "url": "https://promptfax.app/mcp"
    }
  }
}

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

Changelog

Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.

  • 31 Aug 26 0
    • Stability: 0.97 → pass security
  • 30 Aug 26 0
    • Stability: pass → 0.97 functional
  • 26 Aug 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 25 Aug 26 0
    • Stability: 0.97 → pass security
  • 24 Aug 26 +1

    No change was recorded against any check on this day. Stability & Change Management went from 93 to 97. That category is still filling its 30-day observation window: 28 days of observed history at the previous scan, 29 at this one. The score rises as the window fills, whether or not the server changes.

  • 16 Aug 26 0
    • Tool “start_session” rewrote its description, which is the text the model reads security
    • “start_session” reworded the description of “files” cosmetic
  • 11 Aug 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 1 Aug 26 0
    • Authorization: unverified → pass ▲ security
    • Tool coverage: unverified → 100 ▲ functional
    • Stability: unverified → 0.20 ▲ functional
    • MCP protocol: unverified → pass ▲ functional
Diagnostics

Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.

Captured 20 Sept 2026 · Probed https://promptfax.app/mcp

TLS valid

Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .

Subject Issuer Valid from Valid until Key Signature Serial
CN=promptfax.app CN=WR3,O=Google Trust Services,C=US 9 Sept 2026 8 Dec 2026 RSA 2048 SHA256-RSA 41d8034051c49a411092b22007909429
SANs: promptfax.app
CN=WR3,O=Google Trust Services,C=US (CA) CN=GTS Root R1,O=Google Trust Services LLC,C=US 13 Dec 2023 20 Feb 2029 RSA 2048 SHA256-RSA 7ff005a91568d63abc22861684aa4b5a
CN=GTS Root R1,O=Google Trust Services LLC,C=US (CA) CN=GlobalSign Root CA,OU=Root CA,O=GlobalSign nv-sa,C=BE 19 Jun 2020 28 Jan 2028 RSA 4096 SHA256-RSA 77bd0d6cdb36f91aea210fc4f058d30d

Background: What to check on a remote MCP endpoint →

DNSSEC secure

Validation of promptfax.app. — Secure

Zone DS Keys Algorithms Outcome
. trust_anchor 20326, 38696 8, 8 Verified
app. present 23684 8 Verified
promptfax.app. present 2371 13 Verified
promptfax.app. Verified address RRset verified with the apex keys
Authentication Enforced and verified

The endpoint asked for a token and published valid RFC 9728 metadata describing how to get one.

Result Enforced and verified
Enforced On tool calls
HTTP status 200

WWW-Authenticate challenge Bearer realm="promptfax-mcp", resource_metadata="https://promptfax.app/.well-known/oauth-protected-resource/mcp" 

Bearer realm="promptfax-mcp", resource_metadata="https://promptfax.app/.well-known/oauth-protected-resource/mcp"

Protected resource metadata

Document https://promptfax.app/.well-known/oauth-protected-resource/mcp
Retrieved Yes
Resource https://promptfax.app/mcp
Authorisation server https://promptfax.app/

Background: How OAuth 2.1 works in the 2026 MCP spec →

Transports 2 probes
Transport URL Outcome Status Location
streamable-http https://promptfax.app/mcp Verified 200
http (plaintext) http://promptfax.app/mcp HTTPS enforced 301 https://promptfax.app:443/mcp
MCP tools · 8 exposed · ~1,405 tokens

The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →

Tool Tokens
attach_document ~144

Fallback/non-widget tool for binding a PromptFax document or one or more HTTPS PDF URLs into the current MCP session before requesting a quote. In ChatGPT widget sessions, prefer the widget's file controls after start_session instead of calling this tool unless the widget is unavailable or the user explicitly asks for fallback behavior.

NameTypeReqDescription
documentIdstring–PromptFax document identifier created by a prior upload or hosted session.
fileUrlsarray–One or more HTTPS URLs for PDF or image documents that PromptFax should attach to the fax workflow.
sessionIdstringyesPromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

cancel ~83

Use this when you need to cancel the active PromptFax send.

NameTypeReqDescription
sendIntentIdstring–PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

checkout ~172

Fallback/non-widget tool for starting external Stripe Checkout after the user accepts a pay-per-use quote. Payment authorization is required before PromptFax can send; PromptFax treats webhook-confirmed authorization, not browser redirect, as payment truth. In ChatGPT widget sessions, do not call this after start_session because the widget's Pay & send step opens Checkout.

NameTypeReqDescription
autoSendAfterAuthorizationboolean–When true, PromptFax sends automatically after Stripe confirms payment authorization. When false, call send_fax after authorization.
sendIntentIdstring–PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

get_quote ~204

Fallback/non-widget tool for creating a user-reviewable pay-per-use fax quote when you have a fax number and either an MCP session, a PromptFax documentId, or one or more HTTPS PDF URLs. A quote is required before Stripe Checkout and before any real fax transmission. In ChatGPT widget sessions, do not call this after start_session because the widget auto-quotes once the document and destination are ready.

NameTypeReqDescription
documentIdstring–PromptFax document identifier created by a prior upload or hosted session.
faxNumberstring–Destination US fax number. Accepts common human formats such as 415-555-0182 or E.164 format such as +14155550182.
fileUrlsarray–One or more HTTPS URLs for PDF or image documents that PromptFax should attach to the fax workflow.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

get_status ~92

Use this when you need the latest PromptFax workflow state, quote/payment state, or fax transmission status.

NameTypeReqDescription
sendIntentIdstring–PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

retry_failed_fax ~114

Use this after a retry-eligible failed fax to queue another attempt under the existing authorization. You may supply a corrected destination.

NameTypeReqDescription
faxNumberstring–Optional corrected US fax number for this attempt.
sendIntentIdstring–PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

send_fax ~119

Fallback/non-widget tool for sending after payment is authorized and the user explicitly wants to send now. In ChatGPT widget sessions, do not call this after start_session unless the widget is unavailable or the user explicitly asks for fallback behavior.

NameTypeReqDescription
sendIntentIdstring–PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

start_session ~477

Use this first when a user wants to send or price a fax. PromptFax is built for irregular, pay-per-use outbound faxing: every real send requires a user-reviewed quote and Stripe payment authorization before transmission. MCP clients should set hostType to identify their host: chatgpt, claude, browser, or other. In ChatGPT, pass official files[] file parameters first when they are available so PromptFax can immediately import files[].download_url; never pass a raw file_id or local path as the document. The ChatGPT widget opens for destination entry, automatic quote creation, Stripe Checkout, status tracking, and Choose PDF from ChatGPT fallback when automatic attachment is unavailable or fails. If no document is attached, tell the user to attach a document in the widget. The widget does not provide a document preview step. Do not tell ChatGPT users to get a quote; after the widget has a document and valid destination, tell them to verify the price and use Pay & send when ready. Standards-compatible MCP Apps hosts use the inline PromptFax picker, and text-only clients use the hosted PromptFax session page or attach_document with a fetchable HTTPS URL. Do not call get_quote, checkout, or send_fax for a ChatGPT widget session unless the user explicitly asks for fallback behavior or the widget is unavailable. Use get_status only for a textual status refresh.

NameTypeReqDescription
faxNumberstring–Destination US fax number. Accepts common human formats such as 415-555-0182 or E.164 format such as +14155550182.
filesarray–Optional host-supplied files for initial attachment. ChatGPT file parameters include files[].download_url and files[].file_id.
hostCapabilitiesobject–Optional host capability hints, such as whether the client supports widgets, file-picking, hosted links, or other interactive surfaces.
hostTypestring–Identify the MCP host so PromptFax can choose the right interaction mode. Use chatgpt for ChatGPT, claude for Claude, browser for a browser-hosted app, or other for unknown clients.
metadataobject–Optional host-specific metadata for diagnostics or session continuity.
sessionIdstring–PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.

Structured output declared, but exposes no named fields.

No examples provided.

Common questions

What is the PromptFax MCP server?

PromptFax is an MCP server listed in the public MCP registry as app.promptfax/promptfax. Send a one-off fax from inside ChatGPT or Claude. Pay-per-use, $2-$4.50 per delivered fax. This page covers its hosted endpoint (https://promptfax.app/mcp).

Is the PromptFax MCP server safe to use?

PromptFax scores 90 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

What tools does the PromptFax MCP server expose?

PromptFax exposes 8 tools: start_session, attach_document, get_quote, checkout, send_fax, and 3 more. Their descriptions and schemas cost roughly 1,405 tokens of context every time the server is loaded.

Does the PromptFax MCP server require authentication?

Yes. PromptFax asked us for credentials when we connected, so you will need to authorise it in your MCP client before it can do anything.

Is the PromptFax MCP server still maintained?

PromptFax is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.