MCP-CORE v0.1 — the neutral MCP server transport
**Status:** SHIPPED with discipline-core 0.6.0 (MCP-SOVEREIGNTY-PLAN
Wave 2); the flow foundation is named core-ai-native since the
package-family rename (PROP-028), and the crate ships as
core-ai-native-mcp.
The transport every `mcp`-kind package's server builds on:
this package owns what no single language owns, and a JSON-RPC loop is
exactly that.
Consumers: the per-language discipline servers
(`rust-ai-native-mcp`, `typescript-ai-native-mcp`) vendor this crate
byte-identically (sync-engines) and mount their tool sets on it.
**Related:** the consumer-side kind and delivery laws live in the
consuming repo's PROP-027 (`spec://org.vibevm.core/vibevm/modules/vibe-mcp/PROP-027`);
the tcg tool grammar in TCG-PROTOCOL-RUST-v0.1 / TCG-PROTOCOL-v0.1 (the
stacks) is transport-independent and unchanged by this mechanism.
`req r1`
Line-delimited JSON-RPC 2.0 over stdio — one JSON object per line, no
Content-Length framing (that is the LSP convention; MCP hosts speak
lines, and the production vibe-mcp server has spoken exactly this shape
against every supported agent host since PROP-015).
The answered protocol revision is `2024-11-05`.
Inbound frames classify by `id`:
- present-and-non-null = a REQUEST that
MUST be answered;
- absent-or-null = a NOTIFICATION that MUST be absorbed
without a response (hosts send `notifications/initialized` and
cancellations).
A malformed line — non-JSON, or a frame without
`method` — is answered with JSON-RPC `parse error` (-32700) and MUST
NOT kill the loop: the loop ends only at end-of-input or a dead
channel.
Transport-level failure is the layer's one `thiserror` enum,
each variant citing this mechanism and naming a fix surface.
`req r1`
The server is `(name, version, ToolSet)` driven over a `Transport` seam
(`read_line` / `write_line`; production = locked stdio, tests = a
scripted replay double — the whole loop tests with no agent host near
the suite).
Methods:
- `initialize` → `{protocolVersion, serverInfo{name,version},
capabilities:{tools:{listChanged:false}}}`.
- `tools/list` → the registry's descriptors, stable (sorted) order.
- `tools/call` → dispatch by `name` with `arguments`; a missing `name`
is `invalid params` (-32602); an unknown tool is
`method not found` (-32601).
- `ping` → `{}`.
- Anything else → `method not found`.
`req r1`
Everything a tool run says — including CHILD processes (a floor's
cargo, prettier, node) — goes to the process's stderr channel, so the
only capture that sees a whole run is a process-level redirect around
the call: `dup2` over fd 2 on unix, `SetStdHandle(STD_ERROR_HANDLE, …)`
on Windows, into a temp FILE (a file, not a pipe — a filling pipe
blocks the writer and deadlocks a chatty floor).
A threaded
`&mut dyn Write` was rejected at the plan's Wave-0 spike: children
inherit the process handle and bypass it entirely.
Laws: the redirect is process-global, so captures MUST NOT nest or run
concurrently (the loop dispatches tools sequentially — that is the
licence); a second simultaneous capture refuses with this unit cited.
Restoration rides `Drop`, so a panicking tool cannot leave the process
mute.
This cell is the crate's audited home of raw-descriptor
unsafety — nothing else touches fds or std handles.
`req r1`
A server has no interactive channel: tools MUST NOT prompt — anything
that would ask becomes an explicit tool parameter (`force`-class flags
included).
And nothing in this crate knows vibe, a language, or a
discipline rule: a server built on it serves with `vibe` absent from
`PATH` — the consuming repo's PROP-027 §2.6 turns that property into an
acceptance test.