wehub-resource-sync
49b9bb6724
Deploy Docs / deploy-docs (push) Failing after 1s
Conformance Tests / client-conformance (push) Failing after 3s
Conformance Tests / server-conformance (push) Failing after 1s
GitHub Actions Security Analysis / zizmor (push) Failing after 1s
CI / checks (push) Failing after 59m20s
CI / all-green (push) Waiting to run
42 lines
1.7 KiB
Markdown
42 lines
1.7 KiB
Markdown
# extensions
|
|
|
|
Writing your own extension (SEP-2133): one identifier bundles a settings entry
|
|
under `ServerCapabilities.extensions`, a contributed tool, and a vendor request
|
|
method gated on the client declaring the extension back.
|
|
|
|
## Run it
|
|
|
|
```bash
|
|
# stdio (default — the client spawns the server as a subprocess)
|
|
uv run python -m stories.extensions.client
|
|
|
|
# HTTP — the client self-hosts the server on a free port, runs, then tears it down
|
|
uv run python -m stories.extensions.client --http
|
|
```
|
|
|
|
## What to look at
|
|
|
|
- `server.py` `class Catalog(Extension)` — the whole extension: `settings()`
|
|
becomes the advertised capability entry, `tools()` contributes a regular tool,
|
|
`methods()` registers a vendor verb. The extension never holds the server; it
|
|
declares contributions and `MCPServer(extensions=[...])` consumes them.
|
|
- `server.py` `require_client_extension(ctx, EXTENSION_ID)` — the vendor method
|
|
rejects clients that did not declare the extension with `-32021` (missing
|
|
required client capability) and a machine-readable `requiredCapabilities`
|
|
payload.
|
|
- `client.py` `Client(target, extensions=[advertise(EXTENSION_ID)])` — the client-side
|
|
half of the negotiation; on 2026-07-28 it travels in the per-request `_meta`
|
|
envelope.
|
|
- `client.py` `client.session.send_request(...)` — vendor methods have no
|
|
`Client`-level helper; the session escape hatch sends them.
|
|
|
|
## Spec
|
|
|
|
[SEP-2133 — extensions capability](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/2133)
|
|
· [Capabilities — `_meta` key grammar](https://modelcontextprotocol.io/specification/draft/basic/index)
|
|
|
|
## See also
|
|
|
|
`apps/` (the built-in MCP Apps extension) · `custom_methods/` (the same verb
|
|
registered on the lowlevel `Server` by hand, without an extension).
|