hush/internal/web/templates/mcp.html

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<h1>hush<span>.</span> from an agent</h1>
<p class="lede">Two MCP tools. The encryption happens on your machine, so an
  agent using hush gets the same guarantee a browser does.</p>

<table>
  <tr><th>Tool</th><th>What it does</th></tr>
  <tr><td>hush_create</td><td>Encrypts a secret locally, stores the ciphertext, returns a link that works exactly once</td></tr>
  <tr><td>hush_reveal</td><td>Opens a link and destroys it</td></tr>
</table>

<p>It is a local binary rather than an endpoint on this server for one reason: if
  the server did the encrypting, the server could read every secret an agent
  created, and hush's claim would hold for browser users while quietly not
  holding for you. <code>hush-mcp</code> is a peer of the browser — it mints the
  AES-256 key, encrypts, posts only ciphertext, and assembles the
  <code>#fragment</code> link itself.</p>

<h2>1. Install it</h2>
<pre>go install github.com/orchard9/hush/cmd/hush-mcp@latest</pre>
<p>Needs Go 1.26 or newer, and nothing else: the binary imports only the
  standard library, so there is no dependency to resolve and no service to run.</p>

<p>Most clients do not expand <code>~</code>, so get the absolute path once and
  paste that everywhere below:</p>
<pre>echo "$(go env GOPATH)/bin/hush-mcp"</pre>

<h2>2. Register it with your client</h2>
<p>Every client here launches the same binary over stdio. The JSON shape is the
  portable part; only VS Code spells the wrapper key differently.</p>

<h3>Claude Code</h3>
<pre>claude mcp add hush -e HUSH_BASE_URL=https://hush.threesix.ai \
  -- /Users/you/go/bin/hush-mcp</pre>
<p>The <code>--</code> is load-bearing: everything after it is the command to
  launch, so Claude Code stops reading those arguments as its own. Add
  <code>-s user</code> to get the server in every project rather than this one.
  <code>claude mcp list</code> then prints
  <code>hush: … ✔ Connected</code>.</p>

<h3>Codex CLI</h3>
<pre>codex mcp add hush --env HUSH_BASE_URL=https://hush.threesix.ai \
  -- /Users/you/go/bin/hush-mcp</pre>
<p>That writes <code>~/.codex/config.toml</code>. The same thing by hand:</p>
<pre>[mcp_servers.hush]
command = "/Users/you/go/bin/hush-mcp"
env = { "HUSH_BASE_URL" = "https://hush.threesix.ai" }</pre>
<p>Confirm with <code>codex mcp get hush</code>, or <code>/mcp</code> in a
  session.</p>

<h3>Gemini CLI</h3>
<pre>gemini mcp add hush /Users/you/go/bin/hush-mcp \
  -e HUSH_BASE_URL=https://hush.threesix.ai -s user</pre>
<p>Without <code>-s user</code> the entry lands in the current project's
  <code>.gemini/settings.json</code> instead of
  <code>~/.gemini/settings.json</code>. Confirm with <code>/mcp</code> in a
  session.</p>

<h3>VS Code</h3>
<pre>code --add-mcp '{"name":"hush","type":"stdio","command":"/Users/you/go/bin/hush-mcp","env":{"HUSH_BASE_URL":"https://hush.threesix.ai"}}'</pre>
<p>By hand the file is <code>.vscode/mcp.json</code> for one workspace, or the
  user-level <code>mcp.json</code> that <strong>MCP: Open User
  Configuration</strong> opens — and its wrapper key is <code>servers</code>,
  not <code>mcpServers</code>:</p>
<pre>{
  "servers": {
    "hush": {
      "type": "stdio",
      "command": "/Users/you/go/bin/hush-mcp",
      "env": { "HUSH_BASE_URL": "https://hush.threesix.ai" }
    }
  }
}</pre>

<h3>Claude Desktop, Cursor, omp, anything else</h3>
<p>One block, in that client's config file:</p>
<pre>{
  "mcpServers": {
    "hush": {
      "type": "stdio",
      "command": "/Users/you/go/bin/hush-mcp",
      "env": { "HUSH_BASE_URL": "https://hush.threesix.ai" }
    }
  }
}</pre>
<table>
  <tr><th>Client</th><th>File</th></tr>
  <tr><td>Claude Desktop</td><td>macOS <code>~/Library/Application Support/Claude/claude_desktop_config.json</code>, Windows <code>%APPDATA%\Claude\claude_desktop_config.json</code> — then quit the app completely and reopen it</td></tr>
  <tr><td>Cursor</td><td><code>~/.cursor/mcp.json</code> for every project, <code>.cursor/mcp.json</code> for one</td></tr>
  <tr><td>omp</td><td><code>~/.omp/agent/mcp.json</code></td></tr>
</table>
<p>From a clone of the repo, <code>make mcp</code> does the omp case for you: it
  builds the binary, proves the handshake before wiring anything, then rewrites
  only hush's entry — backing the file up and leaving every other server
  alone.</p>

<h2>3. Prove it before you trust it</h2>
<p>A misconfigured stdio server reaches you as an opaque “server disconnected”.
  Run the handshake yourself instead, where the error is legible:</p>
<pre>printf '%s\n' \
  '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{}}}' \
  '{"jsonrpc":"2.0","id":2,"method":"tools/list"}' \
  | /Users/you/go/bin/hush-mcp</pre>
<p>Two JSON lines come back: the first names the server <code>hush</code>, the
  second lists <code>hush_create</code> and <code>hush_reveal</code>. That is
  the same binary, launched the same way, that your client will run.</p>

<h2>4. Use it</h2>
<p>Ask in words; the agent picks the tool.</p>
<ul>
  <li>“Put this in a hush link so I can send it: <em>&lt;the credential&gt;</em>”</li>
  <li>“Open this hush link: <em>https://hush.threesix.ai/s/…#…</em>”</li>
</ul>
<p>Three behaviours worth knowing before an agent calls either tool:</p>
<ul>
  <li><span class="destructive">hush_reveal destroys the link.</span> After it
    returns, the intended recipient cannot open it. An agent that reveals a link
    “just to check” has burned it.</li>
  <li><strong>The link is shown once.</strong> hush cannot rebuild it, because
    the key it carries was never sent to the server.</li>
  <li><strong>The <code>#fragment</code> is the key.</strong> Chat clients and
    mail rewriters truncate fragments, and a link without one carries no key.
    The tool says exactly that, without touching the secret.</li>
</ul>

<h2>Configuration</h2>
<table>
  <tr><th>Variable</th><th>Meaning</th></tr>
  <tr><td>HUSH_BASE_URL</td><td>Which deployment <code>hush_create</code> posts to. Defaults to <code>https://hush.threesix.ai</code></td></tr>
  <tr><td>HUSH_CREATE_TOKEN</td><td>Only for a deployment that has closed anonymous create. Unset is the normal case</td></tr>
</table>
<p><code>hush_reveal</code> ignores both and reveals against the link's own
  origin. A link minted by another hush deployment would be meaningless here,
  and reporting it <em>gone</em> would be a lie about a secret nobody had
  touched.</p>

<h2>When a client will not connect</h2>
<ul>
  <li>Use the absolute path: most clients do not expand <code>~</code>.</li>
  <li>Restart the client. Claude Desktop needs a full quit, not a window close.</li>
  <li>Check the wrapper key — <code>servers</code> in VS Code,
    <code>mcpServers</code> everywhere else.</li>
  <li>Ask the client: <code>claude mcp list</code>,
    <code>codex mcp get hush</code>, or <code>/mcp</code> in a session. VS Code
    logs to <strong>Output → MCP</strong>, Claude Desktop to
    <code>~/Library/Logs/Claude/mcp*.log</code>.</li>
  <li>A <em>gone</em> error is not a connection fault: that link was already
    opened, expired, or never existed. If you did not open it, assume someone
    else did and rotate the secret.</li>
</ul>

<p>Source: <a href="https://github.com/orchard9/hush">github.com/orchard9/hush</a>.</p>
{{end}}

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