🔬 Online MCP Inspector

Connect to any remote MCP endpoint and inspect the live JSON-RPC exchange — Streamable HTTP and legacy SSE supported.

Connection

Not connected.

—

Select a tool

Pick a tool on the left to inspect its schema and run it.

Protocol Log

No traffic yet.

How to test a Streamable HTTP MCP endpoint

Paste the endpoint URL (e.g. https://mcp.deepwiki.com/mcp) and hit ⚡ Connect & Initialize.
The inspector sends an initialize JSON-RPC request with Accept: application/json, text/event-stream and stores the returned Mcp-Session-Id.
It then calls tools/list (and resources/list/prompts/list when advertised) — pick a tool, fill the form, and run it.

Equivalent curl:

curl -X POST https://mcp.deepwiki.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"inspector","version":"1.0"}}}'

Streamable HTTP vs SSE

	Streamable HTTP (2025-03-26)	Legacy HTTP + SSE
Endpoints	One URL for POST (+ optional GET stream)	GET `/sse` + POST message URL
Responses	JSON or SSE per-request	Always via SSE stream
Status	Current spec — use this	Deprecated, still used by some servers

JSON-RPC error codes

Code	Meaning	Typical fix
`-32700`	Parse error	Body isn't valid JSON
`-32600`	Invalid request	Missing jsonrpc/id/method
`-32601`	Method not found	Wrong method name or capability missing
`-32602`	Invalid params	Tool arguments don't match inputSchema
`-32603`	Internal error	Server-side failure
`-32000…-32099`	Server-defined errors	`-32001` = unauthorized in many impls

HTTP status cheat sheet

Status	Meaning	Fix
`401`	OAuth required	Complete the OAuth flow; see OAuth Debugger
`404`	Wrong path	Try /mcp vs /sse vs /v1/mcp
`405`	Method not allowed	Endpoint may be SSE-only or disabled
`406`	Bad Accept header	Send Accept: application/json, text/event-stream
`410`	Endpoint removed	Legacy transport retired — switch to /mcp
`429`	Rate limited	Back off / add auth
`5xx`	Server error	Retry; check provider status