Server Cards: recommend /server-card over .well-known (resolves #12) (#22)

Resolves #12.

## What & why

Moves the **single-server Server Card** off a `.well-known` path. We
reserve `GET <streamable-http-url>/server-card` as the recommended
location while allowing **any unreserved URI** — the Catalog
(`/.well-known/mcp/catalog.json`) is the discovery entrypoint and
already carries each card's `url`, so clients never need to guess where
a card lives.

Adopts wording close to the resolution discussed in #12 (credit: Darrel
Miller's point that `.well-known` is for *site-wide* metadata, not
application-level metadata like an individual server's card; proposed
wording from @SamMorrowDrums and @tadasant):

> MCP Servers MAY host their Server Card at `GET
<streamable-http-url>/server-card`, which we reserve for this purpose,
though any unreserved URI is valid. MCP Servers SHOULD respect the
agreed media type wherever they choose to host it. After a client
identifies a Server Card URL from an AI Catalog or MCP Catalog, it
SHOULD request that URL expressing the Server Card media type.

### Content negotiation

A client fetching a Server Card requests its preferred representation
with the `Accept` header (`Accept: application/mcp-server-card+json`) —
the request-side content-negotiation header for a GET. The server echoes
the type it actually served back in the response's `Content-Type`.

> **Note on media type:** this PR is scoped to *placement* only and does
**not** perform the `application/mcp-server+json` →
`application/mcp-server-card+json` rename — that is handled in a
separate PR. So the two coexist deliberately here:
> - **Pre-existing strings** (catalog-entry description, the four
example `mediaType` values, validation prose, and the "Server Cards use
the media type" line) are left as `application/mcp-server+json`,
untouched, for the rename PR to sweep.
> - **New prose introduced by this PR** (the reserved-location
blockquote and the `Accept`-header example in the "Server Card Location"
section) names the type explicitly as the **post-rename
`application/mcp-server-card+json`**, since the rename PR's diff is
against `main` and would not touch text that doesn't yet exist there.
>
> The temporary mix resolves to a single consistent type once both PRs
land.

## Rationale for `/server-card` (also captured permanently in
`docs/discovery.md` → "Alternatives considered")

- **Not `.well-known`:** site-wide vs. application-level metadata; the
Catalog already provides the `url`, so `.well-known` adds no value for
the card.
- **Not the bare streamable-HTTP endpoint** (`GET <url>` with no
suffix): a GET there already opens the SSE stream in Streamable HTTP.
Hosting the card there overloads the connection-establishing endpoint
and forces content negotiation to disambiguate. Spec-*allowed*,
explicitly **not recommended** — this is the primary motivation for a
distinct suffix.
- **Not domain-root `/mcp/` nesting:** `/mcp` denotes the *transport
endpoint itself* in MCP's canonical-URI examples; there's no precedent
for `/mcp/` as a metadata sub-namespace, and it collides conceptually
with "the JSON-RPC endpoint."
- **Elegant consequence:** because the suffix is appended to the
streamable-HTTP URL, a server at `https://host/mcp` naturally yields
`https://host/mcp/server-card` — path-namespacing for free.

## Scope guardrail

This applies **only to the single-server Server Card**. `.well-known` is
unchanged and remains correct for the **Catalog**
(`/.well-known/mcp/catalog.json`) and OAuth metadata
(`/.well-known/oauth-protected-resource`, etc.) — those are genuinely
site-wide. The doc calls this out explicitly so it doesn't read as
"abandon `.well-known` everywhere."

## Files changed

- **`docs/discovery.md`** — new "Server Card Location" section with the
reserved convention + `Accept`-header guidance; permanent "Alternatives
considered" subsection; rewritten single- and multi-server example URLs
(`https://example.com/mcp/server-card`;
`https://acme.com/code-review/server-card`, `/docs-search/server-card`,
`/ci-cd/server-card`).
- **`schema.ts`** — updated the two `.well-known` doc comments
(`ServerCard` and `Server`) to the new convention.
- **`schema.json`** — regenerated from `schema.ts` (`npm run generate`).
- **`README.md`** — updated the "What is a Server Card?" line to the new
convention, normalizing the pre-existing README-vs-schema `.well-known`
mismatch.

## Verification

- [x] `npm run check` passes (schema.json in sync with schema.ts + `tsc
--noEmit` clean)
- [x] `npm run generate` run and regenerated `schema.json` committed in
the same change
- [x] `npm run validate` passes — all 7 examples validate against the
regenerated schema
- [x] `npm run format` run (prettier clean)
- [x] No single-server-card `.well-known` references remain in
`README.md`, `schema.ts`, `schema.json`, or `docs/discovery.md`
(verified via grep); remaining `.well-known` references are
Catalog/OAuth/the "Alternatives considered" explainer only
- [x] Pre-existing media-type strings left untouched — `git diff
origin/main` shows zero changes to existing
`application/mcp-server+json` strings (rename owned by a separate PR);
only the new placement prose names the post-rename
`application/mcp-server-card+json`
- [x] Examples updated and internally consistent with the new prose
- [x] Fresh-eyes subagent review performed; its one cosmetic finding was
addressed and CI re-confirmed green
- [x] CI green (see checks on this PR)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Agent (Claude) <peter@tadasant.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

schema.ts

@@ -11,7 +11,10 @@
 
 /**
  * A static metadata document describing a remote MCP server, suitable for
- * publishing at a `.well-known/mcp-server-card` URI for pre-connection discovery.
+ * pre-connection discovery. A Server Card MAY be hosted at any unreserved URI;
+ * MCP reserves `GET <streamable-http-url>/server-card` as the recommended
+ * location. Clients learn a card's URL from an MCP/AI Catalog rather than
+ * guessing it.
  *
  * Server Cards intentionally describe only what is needed to discover and
  * connect to a remote server: identity, transport, and protocol versions.
@@ -126,8 +129,9 @@ export interface ServerCard {
  * packages. This is the shape used by the MCP Registry's `server.json`.
  *
  * `Server` documents are typically published to a registry rather than served
- * from a `.well-known` URI, since they may include instructions for installing
- * and executing a server on a client's local machine.
+ * from a Server Card URI (e.g., `<streamable-http-url>/server-card`), since they
+ * may include instructions for installing and executing a server on a client's
+ * local machine.
  *
  * @see [SEP-2127: MCP Server Cards](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2127)
  * @category Server Cards