Visualizers
Learn by moving things
Interactive explainers for the ideas behind retrieval, embeddings, and agents. A formula tells you what is true; dragging a vector shows you why. Each one also appears inside the article it belongs to, and runs entirely in your browser, so drag, poke, and break it.
The six MCP primitives
From: The Six Primitives of MCP →Click each of MCP's six primitives to see who actually controls it, its method, and a plain example. The trap is assuming the server controls everything; it does not.
Actions the model decides to invoke, like sending an email or querying a database.
MCP transports: stdio vs HTTP
From: MCP on the Wire →Same JSON-RPC messages, two channels. Toggle stdio and Streamable HTTP to compare where each runs, how the bytes travel, and what it means for auth.
- Where it runs
- Local subprocess on the same machine
- How bytes travel
- Bytes over stdin / stdout, one long-lived pipe
- Auth
- None needed (same machine, same user)
- Best for
- Desktop apps and local tools (a filesystem or git server)
MCP authorization flow
From: Trust and Authorization in MCP →Step through how a remote MCP server authorizes a call: a 401 pointing at the auth server, an OAuth 2.1 sign-in, a scoped token bound to that one server, then the call. The server never sees your password.