Commons settled on 2026-08-01 that MCP is an extension of the `http` source
family, not a fourth family (`shared/ingest-spec.md` §4). This implements it
with ZERO schema change and zero spec amendment.
The transport discriminator lives in `base_url`, not in new manifest fields:
the shared library rejects unknown manifest keys fail-fast, and we consume it
pull-only at a pinned v0.3.1, so `server_ref`/`tool` as fields would have meant
a spec amendment plus a library release. It buys nothing — the library already
joins `base_url` + `/` + `query`, so `mcp+stdio://<server_ref>` + `<tool>`
reproduces exactly the two-part structure the (now stale) reference plan wanted.
Staying inside the family INHERITS what a fourth family would have had to write
and could have forgotten: the §8 network grant (measured to fire before any tool
call), the `max_rows` cap, §5 verbatim fenced rendering, and the §7 provenance
stamp. The discriminator gates rather than labels — `mcp_get` refuses a URL it
does not own, so an MCP transport can never quietly serve an `https://` manifest
and leave the bundle's provenance claiming a transport that was never used.
Parsing is string-based, not `urlsplit`-based: `urlsplit().hostname` lowercases
the host, which would silently break the case-sensitive env lookup `server_ref`
depends on.
`ingest.py` is untouched — it is AST-guarded mcp-free, so the transport lives in
its own module and is opt-in at the call site. `ingest_mcp.py` imports the open
`mcp` protocol client but never `agent_framework`, keeping the seam D7-portable.
Load-bearing, six mutations all measured RED: detach the scheme guard · make the
refusal unconditional · swap parsing to `urlsplit().hostname` · skip non-text
content instead of raising · force `allow_network=True` · smuggle in a MAF
import. Both source files restored byte-identical (`shasum -c`) after each.
Honesty: `stdio_call_tool` (the real stdio path) is written but never executed
end to end — every test injects a canned tool call, so the suite spawns no
subprocess and opens no socket. No golden fixture, and MCP stays unwired in the
optimiser run path. Stated in docs/extending.md rather than implied away.
555 -> 578 tests; ruff + mypy green.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0112FPR5TX6pDLiNicBPzE8i
Kjell Tore Guttormsen
ddd6338f02