modelcontextprotocol/experimental-ext-interceptors
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Rename mcpserver package to extension, remove *mcp.Server field (#11)

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## Summary

- Rename `interceptors/mcpserver/` → `interceptors/extension/`,
replacing the `Server` wrapper with a lightweight `Extension` that can
install itself on any `*mcp.Server`
- Remove the stored `*mcp.Server` field — `Extension` is now a pure
interceptor container with no server reference
- Add `Install(server)` method to register JSON-RPC methods and init
middleware on a given server
- Update `LocalChain(ctx)` → `LocalChain(ctx, server)` to accept the
server as a parameter
- Remove `MCPServer()`, `Run()`, and `NewStreamableHTTPHandler()`
wrapper methods — users interact with `mcp.Server` directly
- Update all examples, tests, and documentation to use the new API

## Why

`mcpserver.Server` pretended to *be* the server — it had `Run()`,
`NewStreamableHTTPHandler()`, etc. — but it could never cover the full
`*mcp.Server` API, so users constantly needed `MCPServer()` to unwrap
it.

`Extension` doesn't pretend to be the server. It's a pure interceptor
container that can install itself on any server (or multiple servers)
on the fly. No stored server reference, no wrapping, no delegation
surface to maintain.

### Before

```go
mcpServer := mcp.NewServer(...)
srv := mcpserver.NewServer(mcpServer)
srv.AddInterceptor(v)
chain, err := srv.LocalChain(ctx)
```

### After

```go
mcpServer := mcp.NewServer(...)
ext := extension.New()
ext.AddInterceptor(v)
ext.Install(mcpServer)
chain, err := ext.LocalChain(ctx, mcpServer)
```

Signed-off-by: Kurt Degiorgio <kdegiorgio@bloomberg.net>
This commit is contained in:
Kurt Degiorgio 2026-04-30 15:57:18 +01:00 • committed by GitHub
commit 074dc6cdbd
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GPG key ID: B5690EEEBB952194
2 changed files with 172 additions and 173 deletions
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16
go/sdk/examples/mutator/main.go
View file

@ -15,8 +15,8 @@ import (
"github.com/modelcontextprotocol/go-sdk/mcp"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors/extension"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors/integrations/gomiddleware"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors/mcpserver"
)
func main() {
@ -73,13 +73,14 @@ func main() {
},
}
// Create the interceptor server (registers interceptors as discoverable
// Create the interceptor extension (registers interceptors as discoverable
// resources via interceptors/list and interceptor/invoke).
srv := mcpserver.NewServer(mcpServer)
srv.AddInterceptor(m)
ext := extension.New()
ext.AddInterceptor(m)
ext.Install(mcpServer)
// Create a chain connected via in-memory transport.
chain, err := srv.LocalChain(context.Background())
chain, err := ext.LocalChain(context.Background(), mcpServer)
if err != nil {
log.Fatal(err)
}
@ -101,7 +102,10 @@ func main() {
),
)
handler := mcpserver.NewStreamableHTTPHandler(srv, nil)
handler := mcp.NewStreamableHTTPHandler(
func(r *http.Request) *mcp.Server { return mcpServer },
nil,
)
log.Println("listening on :8080")
if err := http.ListenAndServe(":8080", handler); err != nil {
log.Fatal(err)

16
go/sdk/examples/validator/main.go
View file

@ -15,8 +15,8 @@ import (
"github.com/modelcontextprotocol/go-sdk/mcp"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors/extension"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors/integrations/gomiddleware"
"github.com/modelcontextprotocol/ext-interceptors/go/sdk/interceptors/mcpserver"
)
func main() {
@ -70,13 +70,14 @@ func main() {
},
}
// Create the interceptor server (registers interceptors as discoverable
// Create the interceptor extension (registers interceptors as discoverable
// resources via interceptors/list and interceptor/invoke).
srv := mcpserver.NewServer(mcpServer)
srv.AddInterceptor(v)
ext := extension.New()
ext.AddInterceptor(v)
ext.Install(mcpServer)
// Create a chain connected via in-memory transport.
chain, err := srv.LocalChain(context.Background())
chain, err := ext.LocalChain(context.Background(), mcpServer)
if err != nil {
log.Fatal(err)
}
@ -98,7 +99,10 @@ func main() {
),
)
handler := mcpserver.NewStreamableHTTPHandler(srv, nil)
handler := mcp.NewStreamableHTTPHandler(
func(r *http.Request) *mcp.Server { return mcpServer },
nil,
)
log.Println("listening on :8080")
if err := http.ListenAndServe(":8080", handler); err != nil {
log.Fatal(err)