MCP Web Client

April 21, 2026 · View on GitHub

A browser-based example MCP client. Thin UI layer over the Mcp\Client\Client exposed by this SDK — all protocol, transport, OAuth, and session-resumption logic is delegated to the SDK. Designed to drop into shared PHP hosting (cPanel, Apache, PHP-FPM) with no build step.

Important: While this web client is designed to run in a cPanel/Apache web environment, it is never intended to be used on a public facing web site. It's for developers to use internally for experimenting and testing the SDK. The method that developers use to protect the web client from unauthorized access is beyond the scope of this SDK.

Requirements

  • PHP 8.1+ with ext-curl and ext-json
  • Composer
  • A writable webclient/logs/ and webclient/tokens/ directory

The bundled composer.json pins the SDK to dev-main so the webclient always exercises the latest committed SDK code — appropriate for a tool whose purpose is testing SDK behavior. Monolog is required for richer logging; remove it with composer remove monolog/monolog if you prefer the built-in fallback logger.

Deployment

  1. Upload the webclient/ directory to your host (e.g. under public_html/).

  2. From inside the uploaded webclient/ directory, run:

    composer install

    That pulls logiscape/mcp-sdk-php (dev-main) plus Monolog into webclient/vendor/. Re-run it periodically to pick up SDK changes.

  3. Ensure webclient/tokens/ and webclient/logs/ are writable by the PHP user.

  4. Point your browser at webclient/index.php.

Working from a repo checkout

When developing inside a checkout of the SDK repo, you can skip step 2 above — Bootstrap also looks for vendor/autoload.php one level up (dirname(webclient)/vendor/autoload.php), so running composer install at the project root is sufficient.

Feature scope

While the core client included with the SDK aims for full MCP conformance, this webclient is intentionally limited to MCP operations that round-trip cleanly inside a single PHP request. That matches the request/response model of shared hosting and keeps the code small enough to audit.

If you are a MCP server developer and your main goal is to test your server with a fully functional client, the MCP Inspector is better suited for that purpose.

Supported

  • stdio and HTTP/HTTPS transports (auto-detected by URL scheme)
  • OAuth 2.1 via the SDK's OAuthConfiguration + FileTokenStorage, with browser-redirect consent, PKCE, and Dynamic Client Registration
  • prompts: list, get
  • tools: list, call
  • resources: list, read
  • completions: debounced auto-complete inside prompt-argument inputs
  • ping + server-info panel (name, version, negotiated protocol version, advertised capabilities)
  • elicitation preview: server-initiated elicitation/create requests are captured, declined, and rendered as a card next to the tool result so users can see what was asked

Files

index.php           HTML shell — Bootstrap layout + mount points
css/app.css         Layout + component styling
js/
  main.js           DOM bootstrap + module wiring
  api.js            Fetch wrapper for the JSON API
  connection.js     Connect/disconnect/ping + form parsing
  capabilities.js   Prompts/tools/resources list + invoke flows
  forms.js          JSON-Schema → HTML form generator
  results.js        Content-block renderers + elicitation cards
  completions.js    Debounced auto-complete
  logs.js           Internal debug log panel
  oauth.js          Post-redirect OAuth resume driver
api/
  connect.php       POST connect, DELETE disconnect, POST resume_oauth
  execute.php       list_*, get_prompt, call_tool, read_resource, ping
  complete.php      Wraps ClientSession::complete()
  oauth_callback.php OAuth redirect landing page
  logs.php          Tail of the internal log file (optional)
lib/
  Bootstrap.php     Autoload + session + logger + JSON helpers
  SessionStore.php  $_SESSION persistence + OAuth config rebuilder
  SessionTokenStorage.php  Per-PHP-session wrapper around FileTokenStorage
  WebCallbackHandler.php   AuthorizationCallbackInterface → redirect exception
  ElicitationCapture.php   Synchronous onElicit handler (auto-decline)
  WebClientInlineLogger.php  PSR-3 fallback when Monolog isn't installed
test_server.php     Example stdio MCP server for quick experiments

Development

  • Start a dev server: php -S 127.0.0.1:8080 -t webclient
  • Or separately for an MCP HTTP server: php -S 127.0.0.1:8081 examples/simple_server_http.php
  • Then connect the webclient to http://127.0.0.1:8081/

License

MIT — same as the SDK.