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feat: Add support for MCP protocol in core SDK #133

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dcab6b2
feat: Add support for MCP protocol in core SDK
dishaprakash Dec 18, 2025
60bf503
fix tests
dishaprakash Dec 18, 2025
fe43aab
fix tests
dishaprakash Dec 18, 2025
99b2ea7
fix error msg
dishaprakash Dec 18, 2025
3d062b0
add release-please auto update to sdk version
dishaprakash Dec 18, 2025
3bd4b92
fix tests
dishaprakash Dec 18, 2025
8cf91f1
fix tests
dishaprakash Dec 18, 2025
433c436
fix tests
dishaprakash Dec 20, 2025
e0ddb88
fix tests
dishaprakash Dec 23, 2025
54d02e3
fix tests
dishaprakash Dec 23, 2025
0696603
fix error handling
dishaprakash Jan 1, 2026
361d09e
add headers check in e2e test
dishaprakash Jan 5, 2026
c9e4b5c
change tokensources into resolved strings
dishaprakash Jan 6, 2026
156604a
test default mcp
dishaprakash Jan 6, 2026
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3 changes: 3 additions & 0 deletions .github/release-please.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -15,3 +15,6 @@
handleGHRelease: true
packageName: mcp-toolbox-sdk-go
releaseType: go
extraFiles: [
"core/transport/mcp/version.go",
]
66 changes: 45 additions & 21 deletions core/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,17 +17,24 @@ package core
import (
"context"
"fmt"
"log"
"net/http"
"strings"

"github.com/googleapis/mcp-toolbox-sdk-go/core/transport"
mcp20241105 "github.com/googleapis/mcp-toolbox-sdk-go/core/transport/mcp/v20241105"
mcp20250326 "github.com/googleapis/mcp-toolbox-sdk-go/core/transport/mcp/v20250326"
mcp20250618 "github.com/googleapis/mcp-toolbox-sdk-go/core/transport/mcp/v20250618"
"github.com/googleapis/mcp-toolbox-sdk-go/core/transport/toolboxtransport"
"golang.org/x/oauth2"
)

// The synchronous interface for a Toolbox service client.
type ToolboxClient struct {
baseURL string
httpClient *http.Client
protocol Protocol
protocolSet bool
transport transport.Transport
clientHeaderSources map[string]oauth2.TokenSource
defaultToolOptions []ToolOption
defaultOptionsSet bool
Expand All @@ -39,17 +46,19 @@ type ToolboxClient struct {
// Inputs:
// - url: The base URL of the Toolbox server.
// - opts: A variadic list of ClientOption functions to configure the client,
// such as setting a custom http.Client or default headers.
// such as setting a custom http.Client, default headers, or the underlying protocol.
//
// Returns:
//
// A configured *ToolboxClient and a nil error on success, or a nil client
// and an error if configuration fails.
func NewToolboxClient(url string, opts ...ClientOption) (*ToolboxClient, error) {
// Initialize the client with default values.
// We default to ProtocolMCP (the newest version alias) if not overridden.
tc := &ToolboxClient{
baseURL: url,
httpClient: &http.Client{},
protocol: MCP, // Default
clientHeaderSources: make(map[string]oauth2.TokenSource),
defaultToolOptions: []ToolOption{},
}
Expand All @@ -64,7 +73,22 @@ func NewToolboxClient(url string, opts ...ClientOption) (*ToolboxClient, error)
}
}

return tc, nil
// Initialize the Transport based on the selected Protocol.
var transportErr error = nil
switch tc.protocol {
case MCPv20250618:
tc.transport, transportErr = mcp20250618.New(tc.baseURL, tc.httpClient)
case MCPv20250326:
tc.transport, transportErr = mcp20250326.New(tc.baseURL, tc.httpClient)
case MCPv20241105:
tc.transport, transportErr = mcp20241105.New(tc.baseURL, tc.httpClient)
case Toolbox:
tc.transport = toolboxtransport.New(tc.baseURL, tc.httpClient)
default:
return nil, fmt.Errorf("unsupported protocol version: %s", tc.protocol)
}

return tc, transportErr
}

// newToolboxTool is an internal factory method that constructs a
Expand All @@ -87,6 +111,7 @@ func (tc *ToolboxClient) newToolboxTool(
schema ToolSchema,
finalConfig *ToolConfig,
isStrict bool,
tr transport.Transport,
) (*ToolboxTool, []string, []string, error) {

// These will be the parameters that the end-user must provide at invocation time.
Expand Down Expand Up @@ -151,17 +176,12 @@ func (tc *ToolboxClient) newToolboxTool(
finalConfig.AuthTokenSources,
)

if (len(remainingAuthnParams) > 0 || len(remainingAuthzTokens) > 0 || len(tc.clientHeaderSources) > 0) && !strings.HasPrefix(tc.baseURL, "https://") {
log.Println("WARNING: Sending ID token over HTTP. User data may be exposed. Use HTTPS for secure communication.")
}

// Construct the final tool object.
tt := &ToolboxTool{
name: name,
description: schema.Description,
parameters: finalParameters,
invocationURL: fmt.Sprintf("%s/api/tool/%s%s", tc.baseURL, name, toolInvokeSuffix),
httpClient: tc.httpClient,
transport: tr,
authTokenSources: finalConfig.AuthTokenSources,
boundParams: localBoundParams,
requiredAuthnParams: remainingAuthnParams,
Expand Down Expand Up @@ -204,9 +224,14 @@ func (tc *ToolboxClient) LoadTool(name string, ctx context.Context, opts ...Tool
}
}

resolvedHeaders, err := resolveClientHeaders(tc.clientHeaderSources)
if err != nil {
return nil, err
}

// Fetch the manifest for the specified tool.
url := fmt.Sprintf("%s/api/tool/%s", tc.baseURL, name)
manifest, err := loadManifest(ctx, url, tc.httpClient, tc.clientHeaderSources)
manifest, err := tc.transport.GetTool(ctx, name, resolvedHeaders)

if err != nil {
return nil, fmt.Errorf("failed to load tool manifest for '%s': %w", name, err)
}
Expand All @@ -219,7 +244,7 @@ func (tc *ToolboxClient) LoadTool(name string, ctx context.Context, opts ...Tool
}

// Construct the tool from its schema and the final configuration.
tool, usedAuthKeys, usedBoundKeys, err := tc.newToolboxTool(name, schema, finalConfig, true)
tool, usedAuthKeys, usedBoundKeys, err := tc.newToolboxTool(name, schema, finalConfig, true, tc.transport)
if err != nil {
return nil, fmt.Errorf("failed to create toolbox tool from schema for '%s': %w", name, err)
}
Expand Down Expand Up @@ -291,15 +316,14 @@ func (tc *ToolboxClient) LoadToolset(name string, ctx context.Context, opts ...T
}
}

// Determine the manifest URL based on whether a specific toolset name was provided.
var url string
if name == "" {
url = fmt.Sprintf("%s/api/toolset/", tc.baseURL)
} else {
url = fmt.Sprintf("%s/api/toolset/%s", tc.baseURL, name)
}
// Fetch the manifest for the toolset.
manifest, err := loadManifest(ctx, url, tc.httpClient, tc.clientHeaderSources)
resolvedHeaders, err := resolveClientHeaders(tc.clientHeaderSources)
if err != nil {
return nil, err
}

// Fetch Manifest via Transport
manifest, err := tc.transport.ListTools(ctx, name, resolvedHeaders)
if err != nil {
return nil, fmt.Errorf("failed to load toolset manifest for '%s': %w", name, err)
}
Expand All @@ -322,7 +346,7 @@ func (tc *ToolboxClient) LoadToolset(name string, ctx context.Context, opts ...T

for toolName, schema := range manifest.Tools {
// Construct each tool from its schema and the shared configuration.
tool, usedAuthKeys, usedBoundKeys, err := tc.newToolboxTool(toolName, schema, finalConfig, finalConfig.Strict)
tool, usedAuthKeys, usedBoundKeys, err := tc.newToolboxTool(toolName, schema, finalConfig, finalConfig.Strict, tc.transport)
if err != nil {
return nil, fmt.Errorf("failed to create tool '%s': %w", toolName, err)
}
Expand Down
47 changes: 19 additions & 28 deletions core/client_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,11 @@ func TestNewToolboxClient(t *testing.T) {
if client.httpClient.Timeout != 0 {
t.Errorf("expected no timeout, got %v", client.httpClient.Timeout)
}

if client.protocol != ProtocolMCP {
t.Errorf("expected default protocol to be ProtocolMCP, got %v", client.protocol)
}

})

t.Run("Returns error when a nil option is provided", func(t *testing.T) {
Expand Down Expand Up @@ -259,7 +264,7 @@ func TestLoadToolAndLoadToolset(t *testing.T) {
defer server.Close()

t.Run("LoadTool - Success", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
tool, err := client.LoadTool("toolA",
context.Background(),
WithBindParamString("param1", "value1"),
Expand All @@ -274,7 +279,7 @@ func TestLoadToolAndLoadToolset(t *testing.T) {
})

t.Run("LoadTool - Negative Test - Unused bound parameter", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadTool("toolA",
context.Background(),
WithBindParamString("param1", "value1"),
Expand All @@ -289,7 +294,7 @@ func TestLoadToolAndLoadToolset(t *testing.T) {
})

t.Run("LoadToolset - Success with non-strict mode", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
tools, err := client.LoadToolset(
"",
context.Background(),
Expand All @@ -306,7 +311,7 @@ func TestLoadToolAndLoadToolset(t *testing.T) {
})

t.Run("LoadToolset - Negative Test - Unused parameter in non-strict mode", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadToolset(
"",
context.Background(),
Expand All @@ -322,7 +327,7 @@ func TestLoadToolAndLoadToolset(t *testing.T) {
})

t.Run("LoadToolset - Negative Test - Unused parameter in strict mode", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadToolset(
"",
context.Background(),
Expand Down Expand Up @@ -434,7 +439,7 @@ func TestNegativeAndEdgeCases(t *testing.T) {

t.Run("LoadTool fails when a nil ToolOption is provided", func(t *testing.T) {

client, _ := NewToolboxClient(server.URL)
client, _ := NewToolboxClient(server.URL, WithProtocol(Toolbox))
_, err := client.LoadTool("any-tool", context.Background(), nil)
if err == nil {
t.Fatal("Expected an error when a nil option is passed to LoadTool, but got nil")
Expand Down Expand Up @@ -474,7 +479,7 @@ func TestNegativeAndEdgeCases(t *testing.T) {
}))
defer serverWithNoTools.Close()

client, _ := NewToolboxClient(serverWithNoTools.URL, WithHTTPClient(serverWithNoTools.Client()))
client, _ := NewToolboxClient(serverWithNoTools.URL, WithHTTPClient(serverWithNoTools.Client()), WithProtocol(Toolbox))

// This call would panic if the code doesn't check for a nil map.
_, err := client.LoadTool("any-tool", context.Background())
Expand Down Expand Up @@ -567,25 +572,11 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
log.SetOutput(&buf)
defer log.SetOutput(originalOutput)

t.Run("logs warning for HTTP with headers", func(t *testing.T) {
buf.Reset()

client, _ := NewToolboxClient(server.URL,
WithHTTPClient(server.Client()),
)

_, _ = client.LoadTool("toolA", context.Background())

expectedLog := "WARNING: Sending ID token over HTTP"
if !strings.Contains(buf.String(), expectedLog) {
t.Errorf("expected log message '%s' not found in output: '%s'", expectedLog, buf.String())
}
})

t.Run("LoadTool fails when a default option is invalid", func(t *testing.T) {
// Setup client with duplicate default options
client, _ := NewToolboxClient(server.URL,
WithHTTPClient(server.Client()),
WithProtocol(Toolbox),
WithDefaultToolOptions(
WithStrict(true),
WithStrict(false),
Expand All @@ -605,7 +596,7 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
})

t.Run("LoadTool fails when tool is not in the manifest", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadTool("tool-that-does-not-exist", context.Background())

if err == nil {
Expand All @@ -621,7 +612,7 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
errorServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
errorServer.Close()

client, _ := NewToolboxClient(errorServer.URL, WithHTTPClient(errorServer.Client()))
client, _ := NewToolboxClient(errorServer.URL, WithHTTPClient(errorServer.Client()), WithProtocol(Toolbox))
_, err := client.LoadTool("any-tool", context.Background())

if err == nil {
Expand All @@ -633,7 +624,7 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
})

t.Run("LoadTool fails with unused auth tokens", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadTool("toolA", context.Background(),
WithAuthTokenString("unused-auth", "token"), // This auth is not needed by toolA
)
Expand All @@ -646,7 +637,7 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
})

t.Run("LoadTool fails with unused bound parameters", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadTool("toolA", context.Background(),
WithBindParamString("unused-param", "value"), // This param is not defined on toolA
)
Expand All @@ -661,7 +652,7 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
})

t.Run("LoadToolset fails with unused parameters in strict mode", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadToolset(
"",
context.Background(),
Expand All @@ -679,7 +670,7 @@ func TestLoadToolAndLoadToolset_ErrorPaths(t *testing.T) {
})

t.Run("LoadToolset fails with unused parameters in non-strict mode", func(t *testing.T) {
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()))
client, _ := NewToolboxClient(server.URL, WithHTTPClient(server.Client()), WithProtocol(Toolbox))
_, err := client.LoadToolset(
"",
context.Background(),
Expand Down
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