Connect to a Model Context Protocol (MCP) server from your browser, see its tools, resources and prompts, call any tool from a form built from its input schema, and read every JSON-RPC message that goes back and forth. It is free, and there is nothing to install.
How to test an MCP server
- Type the Server address and choose Streamable HTTP or SSE (older).
- Add a Bearer token if the server needs one.
- Press Connect. The lists of Tools, Resources and Prompts fill in for whatever the server supports.
- Pick a tool, fill in its arguments and press Call tool.
- Open the JSON-RPC traffic log to see each request and reply exactly as sent and received.
Streamable HTTP or SSE?
Streamable HTTP is the current MCP transport: every message is a POST to one address, often ending in /mcp, and the server answers with JSON or a short event stream. SSE is the older transport: the client keeps a stream open, usually at /sse, and the server tells it where to post messages. If one does not connect, try the other.
Making your server work from a browser
Browsers only let a page talk to another site if that site agrees. Your server needs to answer OPTIONS requests and send Access-Control-Allow-Origin with this site’s address (or *), Access-Control-Allow-Headers: content-type, authorization, mcp-session-id, mcp-protocol-version, and Access-Control-Expose-Headers: mcp-session-id so the session ID can be read. Local servers on localhost work too, as long as they allow this origin.
What happens when you connect
The tester sends initialize with protocol version 2025-06-18, sends the initialized notification, then asks for tools/list, resources/list and prompts/list for whatever the server says it supports. Calling a tool sends tools/call with the arguments from the form. Every request and reply is shown in the traffic log exactly as sent and received.
Privacy and your token
Requests go directly from your browser to the address you enter, and Snowkit's servers never see them. The bearer token is held in memory for this tab only and is never saved. Only connect to servers you trust, because a tool call runs whatever the server has built.
When it will not connect
- Check the address, including the path such as /mcp or /sse.
- If you see a CORS message, the server needs the headers described above.
- A 401 or 403 reply usually means the token is missing or wrong.
- A page loaded over https cannot call a plain http address on another machine, so use https or a local address.
Questions
Who is this for?
Developers building or checking an MCP server who want a quick look at its tools and replies without setting up a client.
Does it support stdio servers?
No. A browser can only reach servers over HTTP, so use Streamable HTTP or SSE.
Can a tool call change things on my server?
Yes, if the tool is built to. Call tools with care on production servers.