MCP servers, over streamable HTTP

A server is a row with a URL; its tools are discovered by a button and
cached, then offered beside the built-in ones. Written by hand rather than
taken from the reference SDK, because that SDK's transport does its own
connecting -- and the one thing that must not be bypassed is check_url on
every hop. Owning the transport is the point; the framing beside it is the
small part.

Sessions are per call: initialize, initialized, the call, a best-effort
DELETE. Caching one wants an owner, a TTL, eviction, a lock and a shutdown
hook, and the server may expire it under all of that anyway -- ToolContext
is a session-free snapshot precisely so nothing in a tool holds live state.

A server's names and descriptions reach the model as instructions and are
bounded before they do; what it returns is escaped preformatted text, never
markdown. Tools are namespaced per server, so two servers exposing "search"
do not collide and neither shadows a built-in.

Also: a round's calls now run together under a semaphore, results indexed
so each tool turn stays paired with its call, and generation.status names
what is running -- a remote tool is latency-bound, and a silent pause is
what a hang looks like.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -51,6 +51,10 @@ runtime. Clone it, `pip install -e .`, run it.
 - **Web search** — offered to the model as a tool it calls when a question needs
   it. DuckDuckGo out of the box (no account, no key), or point it at your own
   SearXNG, or Firecrawl. The sources stay in the transcript
+- **Your own tools** — describe an HTTP call in the admin area (a schema, a URL
+  template, a secret) and a model can make it. Or add an **MCP server** by URL
+  and its tools appear beside the built-in ones. Both restrictable to groups,
+  and neither can be pointed at your own network unless you say so
 - **Speech in and out** — dictate a message and have replies read aloud, against
   any OpenAI-compatible audio endpoint (whisper.cpp, Speaches, Kokoro…). Each
   person picks their own voice
@@ -79,8 +83,8 @@ runtime. Clone it, `pip install -e .`, run it.
 
 **Planned**
 
-Custom tools and MCP servers · agentic execution (local and over SSH) · image
-generation · OCR for scanned PDFs · semantic search in the library.
+Agentic execution (local and over SSH) · image generation · OCR for scanned
+PDFs · semantic search in the library.
 
 See [PLAN.md](PLAN.md) for what is built, what is not, and why.