platform_info mints dps_…; the model threads it. Go SDK v1.7.0, MCP 2026-07-28.

One server that uses every primitive, runs over both transports, sits behind auth, and is tested end to end, with one annotated trace through all of it

The experimental 2025-11-25 primitive that turns a request into call-now-fetch-later, hand-rolled on the wire because the SDK has not caught up

A server's words flow straight into the model's context. The anatomy of how that becomes an attack, and where the host has to stand to stop it

How a remote server proves who is calling: the discovery chain, resource indicators that bind a token to one server, and the passthrough ban that stops a confused deputy

Structured server logs filtered by severity, and the list_changed notifications that keep a client's view of a server from going stale

The plumbing every MCP primitive shares: how a long call reports progress, how either side cancels one, how a connection is checked, how a list is paged

The server asks a person for input mid-task, with a flat form for ordinary data and a URL handoff for the secrets a form must never touch

The client hands the server a list of directories it is allowed to use, a boundary the server asks for and the client defines and enforces

The protocol inverts. A server asks the client to run the host's model, with no API key of its own and a human able to deny every request

One method that suggests values as a user fills in an argument, and the context field that scopes those suggestions to what is already filled

The third server primitive and the one people misread: templates the user selects, rendered into messages that can embed a server's own resources

The primitive for data the model reads, the counterpart to tools, with URI templates for whole families and live notifications when something changes

Every shape a tool result can take: the five content types, structured output validated against a schema, and the difference between a failed tool and a failed protocol

What the model actually receives when it lists a server's tools, how the schema is built from a Go type, and why a tool's annotations cannot be trusted

A single HTTP path carries the protocol. In 2025-11-25 a session id is optional. In 2026-07-28 it is gone.

The simplest MCP transport, built by hand on both sides with no SDK, plus the stderr rule that silently breaks servers

The 2025-11-25 initialize exchange, hand-rolled in Go against a real server. Later revisions dropped it from the protocol core.

Three message shapes, one error object, and a hundred and fifty lines of Go that every MCP transport is built on

The same tool built both ways: what discovery, schemas, and the callback direction actually cost

The Go SDK never prints the protocol. This post does.