Which MCP transports does the tester support?

Streamable HTTP, both the stateless 2026-07-28 protocol and the stateful revisions up to 2025-11-25, and the deprecated HTTP+SSE transport. Local stdio servers cannot be reached from the Internet.

No. A token you add is sent only to the MCP server's own origin for this one test. It is never stored, logged or shown again.

Can I test a server on localhost or my private network?

No. The tester runs on Port.Tools servers and only connects to public Internet addresses.

MCP Server Tester

Connect to a remote MCP server the way a real client does, and see what it offers and where it breaks the spec.

Streamable HTTP
2026-07-28 stateless
HTTP+SSE (legacy)
OAuth discovery
CORS

What the tester checks

Protocol & transport

Detects the stateless 2026-07-28 protocol (server/discover), stateful Streamable HTTP with initialize and sessions, or the deprecated HTTP+SSE transport, the way the spec tells clients to.

Tools, resources, prompts

Lists everything the server advertises, with pagination, and lints tool names, input schemas, descriptions and annotations. Estimates how much model context the tool definitions cost.

Authorization

On a 401, follows the WWW-Authenticate challenge to protected resource metadata (RFC 9728) and the authorization server (RFC 8414 / OpenID), and checks PKCE S256 and client registration.

Browser readiness

Sends a CORS preflight to see whether browser-based MCP clients can call the server, and whether they can read Mcp-Session-Id.

FAQ

Why does my server work in Claude Desktop but fail here?

Desktop clients can launch local stdio servers. This tester runs on the Internet and can only reach remote HTTP servers on public addresses. Use the server's public URL, usually ending in /mcp (or /sse for older servers).

What do PASS, WARN, FAIL and AUTH REQUIRED mean?

PASS: the server speaks MCP correctly. WARN: it works, with issues worth fixing. FAIL: clients will have trouble connecting or using its tools. AUTH REQUIRED: it asks for authorization first. Add a token to test what is behind it.

Does the tester call my tools?

No. It only lists them, so a test never changes data on your server.