go-sdk/mcp/server_test.go

// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.

package mcp

import (
	"bytes"
	"context"
	"encoding/json"
	"log"
	"log/slog"
	"slices"
	"strings"
	"testing"
	"time"

	"github.com/google/go-cmp/cmp"
	"github.com/google/jsonschema-go/jsonschema"
	"github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2"
)

type testItem struct {
	Name  string
	Value string
}

type testListParams struct {
	Cursor string
}

func (p *testListParams) cursorPtr() *string {
	return &p.Cursor
}

type testListResult struct {
	Items      []*testItem
	NextCursor string
}

func (r *testListResult) nextCursorPtr() *string {
	return &r.NextCursor
}

var allTestItems = []*testItem{
	{"alpha", "val-A"},
	{"bravo", "val-B"},
	{"charlie", "val-C"},
	{"delta", "val-D"},
	{"echo", "val-E"},
	{"foxtrot", "val-F"},
	{"golf", "val-G"},
	{"hotel", "val-H"},
	{"india", "val-I"},
	{"juliet", "val-J"},
	{"kilo", "val-K"},
}

// getCursor encodes a string input into a URL-safe base64 cursor,
// fatally logging any encoding errors.
func getCursor(input string) string {
	cursor, err := encodeCursor(input)
	if err != nil {
		log.Fatalf("encodeCursor(%s) error = %v", input, err)
	}
	return cursor
}

func TestServerPaginateBasic(t *testing.T) {
	testCases := []struct {
		name           string
		initialItems   []*testItem
		inputCursor    string
		inputPageSize  int
		wantFeatures   []*testItem
		wantNextCursor string
		wantErr        bool
	}{
		{
			name:           "FirstPage_DefaultSize_Full",
			initialItems:   allTestItems,
			inputCursor:    "",
			inputPageSize:  5,
			wantFeatures:   allTestItems[0:5],
			wantNextCursor: getCursor("echo"), // Based on last item of first page
			wantErr:        false,
		},
		{
			name:           "SecondPage_DefaultSize_Full",
			initialItems:   allTestItems,
			inputCursor:    getCursor("echo"),
			inputPageSize:  5,
			wantFeatures:   allTestItems[5:10],
			wantNextCursor: getCursor("juliet"), // Based on last item of second page
			wantErr:        false,
		},
		{
			name:           "SecondPage_DefaultSize_Full_OutOfOrder",
			initialItems:   append(allTestItems[5:], allTestItems[0:5]...),
			inputCursor:    getCursor("echo"),
			inputPageSize:  5,
			wantFeatures:   allTestItems[5:10],
			wantNextCursor: getCursor("juliet"), // Based on last item of second page
			wantErr:        false,
		},
		{
			name:           "SecondPage_DefaultSize_Full_Duplicates",
			initialItems:   append(allTestItems, allTestItems[0:5]...),
			inputCursor:    getCursor("echo"),
			inputPageSize:  5,
			wantFeatures:   allTestItems[5:10],
			wantNextCursor: getCursor("juliet"), // Based on last item of second page
			wantErr:        false,
		},
		{
			name:           "LastPage_Remaining",
			initialItems:   allTestItems,
			inputCursor:    getCursor("juliet"),
			inputPageSize:  5,
			wantFeatures:   allTestItems[10:11], // Only 1 item left
			wantNextCursor: "",                  // No more pages
			wantErr:        false,
		},
		{
			name:           "PageSize_1",
			initialItems:   allTestItems,
			inputCursor:    "",
			inputPageSize:  1,
			wantFeatures:   allTestItems[0:1],
			wantNextCursor: getCursor("alpha"),
			wantErr:        false,
		},
		{
			name:           "PageSize_All",
			initialItems:   allTestItems,
			inputCursor:    "",
			inputPageSize:  len(allTestItems), // Page size equals total
			wantFeatures:   allTestItems,
			wantNextCursor: "", // No more pages
			wantErr:        false,
		},
		{
			name:           "PageSize_LargerThanAll",
			initialItems:   allTestItems,
			inputCursor:    "",
			inputPageSize:  len(allTestItems) + 5, // Page size larger than total
			wantFeatures:   allTestItems,
			wantNextCursor: "",
			wantErr:        false,
		},
		{
			name:           "EmptySet",
			initialItems:   nil,
			inputCursor:    "",
			inputPageSize:  5,
			wantFeatures:   nil,
			wantNextCursor: "",
			wantErr:        false,
		},
		{
			name:           "InvalidCursor",
			initialItems:   allTestItems,
			inputCursor:    "not-a-valid-gob-base64-cursor",
			inputPageSize:  5,
			wantFeatures:   nil, // Should be nil for error cases
			wantNextCursor: "",
			wantErr:        true,
		},
		{
			name:           "AboveNonExistentID",
			initialItems:   allTestItems,
			inputCursor:    getCursor("dne"), // A UID that doesn't exist
			inputPageSize:  5,
			wantFeatures:   allTestItems[4:9], // Should return elements above UID.
			wantNextCursor: getCursor("india"),
			wantErr:        false,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			fs := newFeatureSet(func(t *testItem) string { return t.Name })
			fs.add(tc.initialItems...)
			params := &testListParams{Cursor: tc.inputCursor}
			gotResult, err := paginateList(fs, tc.inputPageSize, params, &testListResult{}, func(res *testListResult, items []*testItem) {
				res.Items = items
			})
			if (err != nil) != tc.wantErr {
				t.Errorf("paginateList(%s) error, got %v, wantErr %v", tc.name, err, tc.wantErr)
			}
			if tc.wantErr {
				return
			}
			if diff := cmp.Diff(tc.wantFeatures, gotResult.Items); diff != "" {
				t.Errorf("paginateList(%s) mismatch (-want +got):\n%s", tc.name, diff)
			}
			if tc.wantNextCursor != gotResult.NextCursor {
				t.Errorf("paginateList(%s) nextCursor, got %v, want %v", tc.name, gotResult.NextCursor, tc.wantNextCursor)
			}
		})
	}
}

func TestServerPaginateVariousPageSizes(t *testing.T) {
	fs := newFeatureSet(func(t *testItem) string { return t.Name })
	fs.add(allTestItems...)
	// Try all possible page sizes, ensuring we get the correct list of items.
	for pageSize := 1; pageSize < len(allTestItems)+1; pageSize++ {
		var gotItems []*testItem
		var nextCursor string
		wantChunks := slices.Collect(slices.Chunk(allTestItems, pageSize))
		index := 0
		// Iterate through all pages, comparing sub-slices to the paginated list.
		for {
			params := &testListParams{Cursor: nextCursor}
			gotResult, err := paginateList(fs, pageSize, params, &testListResult{}, func(res *testListResult, items []*testItem) {
				res.Items = items
			})
			if err != nil {
				t.Fatalf("paginateList() unexpected error for pageSize %d, cursor %q: %v", pageSize, nextCursor, err)
			}
			if diff := cmp.Diff(wantChunks[index], gotResult.Items); diff != "" {
				t.Errorf("paginateList mismatch (-want +got):\n%s", diff)
			}
			gotItems = append(gotItems, gotResult.Items...)
			nextCursor = gotResult.NextCursor
			if nextCursor == "" {
				break
			}
			index++
		}

		if len(gotItems) != len(allTestItems) {
			t.Fatalf("paginateList() returned %d items, want %d", len(allTestItems), len(gotItems))
		}
	}
}

func TestServerCapabilities(t *testing.T) {
	tool := &Tool{Name: "t", InputSchema: &jsonschema.Schema{Type: "object"}}
	testCases := []struct {
		name             string
		configureServer  func(s *Server)
		serverOpts       ServerOptions
		wantCapabilities *ServerCapabilities
	}{
		{
			name:            "no capabilities",
			configureServer: func(s *Server) {},
			wantCapabilities: &ServerCapabilities{
				Logging: &LoggingCapabilities{},
			},
		},
		{
			name: "with prompts",
			configureServer: func(s *Server) {
				s.AddPrompt(&Prompt{Name: "p"}, nil)
			},
			wantCapabilities: &ServerCapabilities{
				Logging: &LoggingCapabilities{},
				Prompts: &PromptCapabilities{ListChanged: true},
			},
		},
		{
			name: "with resources",
			configureServer: func(s *Server) {
				s.AddResource(&Resource{URI: "file:///r"}, nil)
			},
			wantCapabilities: &ServerCapabilities{
				Logging:   &LoggingCapabilities{},
				Resources: &ResourceCapabilities{ListChanged: true},
			},
		},
		{
			name: "with resource templates",
			configureServer: func(s *Server) {
				s.AddResourceTemplate(&ResourceTemplate{URITemplate: "file:///rt"}, nil)
			},
			wantCapabilities: &ServerCapabilities{
				Logging:   &LoggingCapabilities{},
				Resources: &ResourceCapabilities{ListChanged: true},
			},
		},
		{
			name: "with resource subscriptions",
			configureServer: func(s *Server) {
				s.AddResourceTemplate(&ResourceTemplate{URITemplate: "file:///rt"}, nil)
			},
			serverOpts: ServerOptions{
				SubscribeHandler: func(context.Context, *SubscribeRequest) error {
					return nil
				},
				UnsubscribeHandler: func(context.Context, *UnsubscribeRequest) error {
					return nil
				},
			},
			wantCapabilities: &ServerCapabilities{
				Logging:   &LoggingCapabilities{},
				Resources: &ResourceCapabilities{ListChanged: true, Subscribe: true},
			},
		},
		{
			name: "with tools",
			configureServer: func(s *Server) {
				s.AddTool(tool, nil)
			},
			wantCapabilities: &ServerCapabilities{
				Logging: &LoggingCapabilities{},
				Tools:   &ToolCapabilities{ListChanged: true},
			},
		},
		{
			name:            "with completions",
			configureServer: func(s *Server) {},
			serverOpts: ServerOptions{
				CompletionHandler: func(context.Context, *CompleteRequest) (*CompleteResult, error) {
					return nil, nil
				},
			},
			wantCapabilities: &ServerCapabilities{
				Logging:     &LoggingCapabilities{},
				Completions: &CompletionCapabilities{},
			},
		},
		{
			name: "all capabilities",
			configureServer: func(s *Server) {
				s.AddPrompt(&Prompt{Name: "p"}, nil)
				s.AddResource(&Resource{URI: "file:///r"}, nil)
				s.AddResourceTemplate(&ResourceTemplate{URITemplate: "file:///rt"}, nil)
				s.AddTool(tool, nil)
			},
			serverOpts: ServerOptions{
				SubscribeHandler: func(context.Context, *SubscribeRequest) error {
					return nil
				},
				UnsubscribeHandler: func(context.Context, *UnsubscribeRequest) error {
					return nil
				},
				CompletionHandler: func(context.Context, *CompleteRequest) (*CompleteResult, error) {
					return nil, nil
				},
			},
			wantCapabilities: &ServerCapabilities{
				Completions: &CompletionCapabilities{},
				Logging:     &LoggingCapabilities{},
				Prompts:     &PromptCapabilities{ListChanged: true},
				Resources:   &ResourceCapabilities{ListChanged: true, Subscribe: true},
				Tools:       &ToolCapabilities{ListChanged: true},
			},
		},
		{
			name:            "has features",
			configureServer: func(s *Server) {},
			serverOpts: ServerOptions{
				HasPrompts:   true,
				HasResources: true,
				HasTools:     true,
			},
			wantCapabilities: &ServerCapabilities{
				Logging:   &LoggingCapabilities{},
				Prompts:   &PromptCapabilities{ListChanged: true},
				Resources: &ResourceCapabilities{ListChanged: true},
				Tools:     &ToolCapabilities{ListChanged: true},
			},
		},
		{
			name:            "empty capabilities",
			configureServer: func(s *Server) {},
			serverOpts: ServerOptions{
				Capabilities: &ServerCapabilities{},
			},
			wantCapabilities: &ServerCapabilities{},
		},
		{
			name:            "no logging",
			configureServer: func(s *Server) {},
			serverOpts: ServerOptions{
				Capabilities: &ServerCapabilities{
					Tools: &ToolCapabilities{ListChanged: true},
				},
			},
			wantCapabilities: &ServerCapabilities{
				Tools: &ToolCapabilities{ListChanged: true},
			},
		},
		{
			name:            "no list",
			configureServer: func(s *Server) {},
			serverOpts: ServerOptions{
				Capabilities: &ServerCapabilities{
					Tools:   &ToolCapabilities{ListChanged: false},
					Prompts: &PromptCapabilities{ListChanged: false},
				},
			},
			wantCapabilities: &ServerCapabilities{
				Tools:   &ToolCapabilities{ListChanged: false},
				Prompts: &PromptCapabilities{ListChanged: false},
			},
		},
		{
			name: "adding tools-list",
			configureServer: func(s *Server) {
				s.AddTool(tool, nil)
			},
			serverOpts: ServerOptions{
				Capabilities: &ServerCapabilities{
					Logging: &LoggingCapabilities{},
				},
			},
			wantCapabilities: &ServerCapabilities{
				Logging: &LoggingCapabilities{},
				Tools:   &ToolCapabilities{ListChanged: true},
			},
		},
		{
			name: "adding tools-no list",
			configureServer: func(s *Server) {
				s.AddTool(tool, nil)
			},
			serverOpts: ServerOptions{
				Capabilities: &ServerCapabilities{
					Tools: &ToolCapabilities{ListChanged: false},
				},
			},
			wantCapabilities: &ServerCapabilities{
				Tools: &ToolCapabilities{ListChanged: false},
			},
		},
		{
			name:            "experimental preserved",
			configureServer: func(s *Server) {},
			serverOpts: ServerOptions{
				Capabilities: &ServerCapabilities{
					Experimental: map[string]any{"custom": "value"},
					Logging:      &LoggingCapabilities{},
				},
			},
			wantCapabilities: &ServerCapabilities{
				Experimental: map[string]any{"custom": "value"},
				Logging:      &LoggingCapabilities{},
			},
		},
		{
			name:            "extensions preserved",
			configureServer: func(s *Server) {},
			serverOpts: func() ServerOptions {
				caps := &ServerCapabilities{
					Logging: &LoggingCapabilities{},
				}
				caps.AddExtension("io.example/ext1", map[string]any{"key": "value"})
				caps.AddExtension("io.example/ext2", nil)
				return ServerOptions{Capabilities: caps}
			}(),
			wantCapabilities: &ServerCapabilities{
				Extensions: map[string]any{
					"io.example/ext1": map[string]any{"key": "value"},
					"io.example/ext2": map[string]any{},
				},
				Logging: &LoggingCapabilities{},
			},
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			server := NewServer(testImpl, &tc.serverOpts)
			tc.configureServer(server)
			gotCapabilities := server.capabilities()
			if diff := cmp.Diff(tc.wantCapabilities, gotCapabilities); diff != "" {
				t.Errorf("capabilities() mismatch (-want +got):\n%s", diff)
			}
		})
	}
}

func TestServerAddResourceTemplate(t *testing.T) {
	tests := []struct {
		name        string
		template    string
		expectPanic bool
	}{
		{"ValidFileTemplate", "file:///{a}/{b}", false},
		{"ValidCustomScheme", "myproto:///{a}", false},
		{"EmptyVariable", "file:///{}/{b}", true},
		{"UnclosedVariable", "file:///{a", true},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			rt := ResourceTemplate{URITemplate: tt.template}

			defer func() {
				if r := recover(); r != nil {
					if !tt.expectPanic {
						t.Errorf("%s: unexpected panic: %v", tt.name, r)
					}
				} else {
					if tt.expectPanic {
						t.Errorf("%s: expected panic but did not panic", tt.name)
					}
				}
			}()

			s := NewServer(testImpl, nil)
			s.AddResourceTemplate(&rt, nil)
		})
	}
}

// panicks reports whether f() panics.
func panics(f func()) (b bool) {
	defer func() {
		b = recover() != nil
	}()
	f()
	return false
}

func TestAddTool(t *testing.T) {
	// AddTool should panic if In or Out are not JSON objects.
	s := NewServer(testImpl, nil)
	if !panics(func() {
		AddTool(s, &Tool{Name: "T1"}, func(context.Context, *CallToolRequest, string) (*CallToolResult, any, error) { return nil, nil, nil })
	}) {
		t.Error("bad In: expected panic")
	}
	if panics(func() {
		AddTool(s, &Tool{Name: "T2"}, func(context.Context, *CallToolRequest, map[string]any) (*CallToolResult, any, error) {
			return nil, nil, nil
		})
	}) {
		t.Error("good In: expected no panic")
	}
	if !panics(func() {
		AddTool(s, &Tool{Name: "T2"}, func(context.Context, *CallToolRequest, map[string]any) (*CallToolResult, int, error) {
			return nil, 0, nil
		})
	}) {
		t.Error("bad Out: expected panic")
	}
}

func TestAddToolNameValidation(t *testing.T) {
	tests := []struct {
		label             string
		name              string
		wantLogContaining string
	}{
		{
			label:             "empty name",
			name:              "",
			wantLogContaining: `tool name cannot be empty`,
		},
		{
			label:             "long name",
			name:              strings.Repeat("a", 129),
			wantLogContaining: "exceeds maximum length of 128 characters",
		},
		{
			label:             "name with spaces",
			name:              "get user profile",
			wantLogContaining: `tool name contains invalid characters: \" \"`,
		},
		{
			label:             "name with multiple invalid chars",
			name:              "user name@domain,com",
			wantLogContaining: `tool name contains invalid characters: \" \", \"@\", \",\"`,
		},
		{
			label:             "name with unicode",
			name:              "tool-ñame",
			wantLogContaining: `tool name contains invalid characters: \"ñ\"`,
		},
		{
			label:             "valid name",
			name:              "valid-tool_name.123",
			wantLogContaining: "", // No log expected
		},
	}
	for _, test := range tests {
		t.Run(test.label, func(t *testing.T) {
			var buf bytes.Buffer
			s := NewServer(testImpl, &ServerOptions{
				Logger: slog.New(slog.NewTextHandler(&buf, nil)),
			})

			// Use the generic AddTool as it also calls validateToolName.
			AddTool(s, &Tool{Name: test.name}, func(context.Context, *CallToolRequest, any) (*CallToolResult, any, error) {
				return nil, nil, nil
			})

			logOutput := buf.String()
			if test.wantLogContaining != "" {
				if !strings.Contains(logOutput, test.wantLogContaining) {
					t.Errorf("log output =\n%s\nwant containing %q", logOutput, test.wantLogContaining)
				}
			} else {
				if logOutput != "" {
					t.Errorf("expected empty log output, got %q", logOutput)
				}
			}
		})
	}
}

type schema = jsonschema.Schema

func testToolForSchema[In, Out any](t *testing.T, tool *Tool, in string, out Out, wantIn, wantOut any, wantErrContaining string) {
	t.Helper()
	th := func(context.Context, *CallToolRequest, In) (*CallToolResult, Out, error) {
		return nil, out, nil
	}
	gott, goth, err := toolForErr(tool, th, nil)
	if err != nil {
		t.Fatal(err)
	}
	if diff := cmp.Diff(wantIn, gott.InputSchema); diff != "" {
		t.Errorf("input: mismatch (-want, +got):\n%s", diff)
	}
	if diff := cmp.Diff(wantOut, gott.OutputSchema); diff != "" {
		t.Errorf("output: mismatch (-want, +got):\n%s", diff)
	}
	ctr := &CallToolRequest{
		Params: &CallToolParamsRaw{
			Arguments: json.RawMessage(in),
		},
	}
	result, err := goth(context.Background(), ctr)
	if wantErrContaining != "" {
		// Input validation errors are returned as tool results with IsError=true,
		// not as Go errors. Check both possibilities.
		if err != nil {
			if !strings.Contains(err.Error(), wantErrContaining) {
				t.Errorf("got error %q, want containing %q", err, wantErrContaining)
			}
		} else if result != nil && result.IsError {
			text := result.Content[0].(*TextContent).Text
			if !strings.Contains(text, wantErrContaining) {
				t.Errorf("got tool error %q, want containing %q", text, wantErrContaining)
			}
		} else {
			t.Errorf("got no error, want error containing %q", wantErrContaining)
		}
	} else if err != nil {
		t.Errorf("got error %v, want no error", err)
	}

	if gott.OutputSchema != nil && err == nil && !result.IsError {
		// Check that structured content matches exactly.
		unstructured := result.Content[0].(*TextContent).Text
		structured := string(result.StructuredContent.(json.RawMessage))
		if diff := cmp.Diff(unstructured, structured); diff != "" {
			t.Errorf("Unstructured content does not match structured content exactly (-unstructured +structured):\n%s", diff)
		}
	}
}

// TestClientRootCapabilities verifies that the server correctly observes
// RootsV2 for various client capability configurations. This tests the fix
// for #607.
func TestClientRootCapabilities(t *testing.T) {
	testCases := []struct {
		name         string
		capabilities *string // JSON for the capabilities field; nil means omit the field
		wantRootsV2  *RootCapabilities
	}{
		{
			name:         "capabilities field omitted",
			capabilities: nil,
			wantRootsV2:  nil,
		},
		{
			name:         "empty capabilities",
			capabilities: ptr(`{}`),
			wantRootsV2:  nil,
		},
		{
			name:         "capabilities with no roots",
			capabilities: ptr(`{"sampling": {}}`),
			wantRootsV2:  nil,
		},
		{
			name:         "capabilities with empty roots",
			capabilities: ptr(`{"roots": {}}`),
			wantRootsV2:  &RootCapabilities{ListChanged: false},
		},
		{
			name:         "capabilities with roots without listChanged",
			capabilities: ptr(`{"roots": {"listChanged": false}}`),
			wantRootsV2:  &RootCapabilities{ListChanged: false},
		},
		{
			name:         "capabilities with roots with listChanged",
			capabilities: ptr(`{"roots": {"listChanged": true}}`),
			wantRootsV2:  &RootCapabilities{ListChanged: true},
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			ctx := context.Background()

			// Create a minimal server.
			impl := &Implementation{Name: "testServer", Version: "v1.0.0"}
			s := NewServer(impl, nil)

			// Connect the server.
			cTransport, sTransport := NewInMemoryTransports()
			ss, err := s.Connect(ctx, sTransport, nil)
			if err != nil {
				t.Fatal(err)
			}

			// Connect the client JSON-RPC connection (raw, no client).
			cConn, err := cTransport.Connect(ctx)
			if err != nil {
				t.Fatal(err)
			}

			// Build initialize params, optionally including capabilities.
			var initParams json.RawMessage
			if tc.capabilities != nil {
				initParams = json.RawMessage(`{
					"protocolVersion": "2025-11-25",
					"capabilities": ` + *tc.capabilities + `,
					"clientInfo": {"name": "TestClient", "version": "1.0.0"}
				}`)
			} else {
				initParams = json.RawMessage(`{
					"protocolVersion": "2025-11-25",
					"clientInfo": {"name": "TestClient", "version": "1.0.0"}
				}`)
			}

			initReq, err := jsonrpc2.NewCall(jsonrpc2.Int64ID(1), "initialize", initParams)
			if err != nil {
				t.Fatal(err)
			}

			if err := cConn.Write(ctx, initReq); err != nil {
				t.Fatalf("Write failed: %v", err)
			}

			// Read the initialize response.
			msg, err := cConn.Read(ctx)
			if err != nil {
				t.Fatalf("Read failed: %v", err)
			}
			resp, ok := msg.(*jsonrpc2.Response)
			if !ok {
				t.Fatalf("expected Response, got %T", msg)
			}
			if resp.Error != nil {
				t.Fatalf("initialize failed: %v", resp.Error)
			}

			// Verify that the server session has the correct RootsV2 value.
			params := ss.InitializeParams()
			if params == nil {
				t.Fatal("InitializeParams is nil")
			}

			var gotRootsV2 *RootCapabilities
			if params.Capabilities != nil {
				gotRootsV2 = params.Capabilities.RootsV2
			}
			if diff := cmp.Diff(tc.wantRootsV2, gotRootsV2); diff != "" {
				t.Errorf("RootsV2 mismatch (-want +got):\n%s", diff)
			}

			// Close the client connection.
			if err := cConn.Close(); err != nil {
				t.Fatalf("Stream.Close failed: %v", err)
			}
			ss.Wait()
		})
	}
}

// TODO: move this to tool_test.go
func TestToolForSchemas(t *testing.T) {
	// Validate that toolForErr handles schemas properly.
	type in struct {
		P int `json:"p,omitempty"`
	}
	type out struct {
		B bool `json:"b,omitempty"`
	}

	var (
		falseSchema = &schema{Not: &schema{}}
		inSchema    = &schema{
			Type:                 "object",
			AdditionalProperties: falseSchema,
			Properties:           map[string]*schema{"p": {Type: "integer"}},
			PropertyOrder:        []string{"p"},
		}
		inSchema2 = &schema{
			Type:                 "object",
			AdditionalProperties: falseSchema,
			Properties:           map[string]*schema{"p": {Type: "string"}},
		}
		inSchema3 = &schema{
			Type:                 "object",
			AdditionalProperties: falseSchema,
			Properties:           map[string]*schema{}, // empty map is preserved
		}
		outSchema = &schema{
			Type:                 "object",
			AdditionalProperties: falseSchema,
			Properties:           map[string]*schema{"b": {Type: "boolean"}},
			PropertyOrder:        []string{"b"},
		}
		outSchema2 = &schema{
			Type:                 "object",
			AdditionalProperties: falseSchema,
			Properties:           map[string]*schema{"b": {Type: "integer"}},
			PropertyOrder:        []string{"b"},
		}
	)

	// Infer both schemas.
	testToolForSchema[in](t, &Tool{}, `{"p":3}`, out{true}, inSchema, outSchema, "")
	// Validate the input schema: expect an error if it's wrong.
	// We can't test that the output schema is validated, because it's typed.
	testToolForSchema[in](t, &Tool{}, `{"p":"x"}`, out{true}, inSchema, outSchema, `want "integer"`)
	// Ignore type any for output.
	testToolForSchema[in, any](t, &Tool{}, `{"p":3}`, 0, inSchema, nil, "")
	// Input is still validated.
	testToolForSchema[in, any](t, &Tool{}, `{"p":"x"}`, 0, inSchema, nil, `want "integer"`)
	// Tool sets input schema: that is what's used.
	testToolForSchema[in, any](t, &Tool{InputSchema: inSchema2}, `{"p":3}`, 0, inSchema2, nil, `want "string"`)
	// Tool sets input schema, empty properties map.
	testToolForSchema[in, any](t, &Tool{InputSchema: inSchema3}, `{}`, 0, inSchema3, nil, "")
	// Tool sets output schema: that is what's used, and validation happens.
	testToolForSchema[in, any](t, &Tool{OutputSchema: outSchema2}, `{"p":3}`, out{true},
		inSchema, outSchema2, `want "integer"`)

	// Check a slightly more complicated case.
	type weatherOutput struct {
		Summary string
		AsOf    time.Time
		Source  string
	}
	testToolForSchema[any](t, &Tool{}, `{}`, weatherOutput{},
		&schema{Type: "object"},
		&schema{
			Type:                 "object",
			Required:             []string{"Summary", "AsOf", "Source"},
			AdditionalProperties: falseSchema,
			Properties: map[string]*schema{
				"Summary": {Type: "string"},
				"AsOf":    {Type: "string"},
				"Source":  {Type: "string"},
			},
			PropertyOrder: []string{"Summary", "AsOf", "Source"},
		},
		"")
}

// TestServerCapabilitiesOverWire verifies that server capabilities are
// correctly sent over the wire during initialization.
func TestServerCapabilitiesOverWire(t *testing.T) {
	tool := &Tool{Name: "test-tool", InputSchema: &jsonschema.Schema{Type: "object"}}

	testCases := []struct {
		name             string
		serverOpts       *ServerOptions
		configureServer  func(s *Server)
		wantCapabilities *ServerCapabilities
	}{
		{
			name:            "Default capabilities",
			serverOpts:      nil,
			configureServer: func(s *Server) {},
			wantCapabilities: &ServerCapabilities{
				Logging: &LoggingCapabilities{},
			},
		},
		{
			name: "Custom Capabilities with tools",
			serverOpts: &ServerOptions{
				Capabilities: &ServerCapabilities{
					Tools: &ToolCapabilities{ListChanged: false},
				},
			},
			configureServer: func(s *Server) {},
			wantCapabilities: &ServerCapabilities{
				Tools: &ToolCapabilities{ListChanged: false},
			},
		},
		{
			name: "Dynamic tool capability",
			serverOpts: &ServerOptions{
				Capabilities: &ServerCapabilities{
					Logging: &LoggingCapabilities{},
				},
			},
			configureServer: func(s *Server) {
				s.AddTool(tool, nil)
			},
			wantCapabilities: &ServerCapabilities{
				Logging: &LoggingCapabilities{},
				Tools:   &ToolCapabilities{ListChanged: true},
			},
		},
		{
			name: "Extensions over wire",
			serverOpts: func() *ServerOptions {
				caps := &ServerCapabilities{
					Logging: &LoggingCapabilities{},
				}
				caps.AddExtension("io.example/ext", map[string]any{"key": "value"})
				return &ServerOptions{Capabilities: caps}
			}(),
			configureServer: func(s *Server) {},
			wantCapabilities: &ServerCapabilities{
				Extensions: map[string]any{
					"io.example/ext": map[string]any{"key": "value"},
				},
				Logging: &LoggingCapabilities{},
			},
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			ctx := context.Background()

			// Create server.
			impl := &Implementation{Name: "testServer", Version: "v1.0.0"}
			server := NewServer(impl, tc.serverOpts)
			tc.configureServer(server)

			// Connect client and server.
			cTransport, sTransport := NewInMemoryTransports()
			ss, err := server.Connect(ctx, sTransport, nil)
			if err != nil {
				t.Fatal(err)
			}
			defer ss.Close()

			client := NewClient(&Implementation{Name: "testClient", Version: "v1.0.0"}, nil)
			cs, err := client.Connect(ctx, cTransport, nil)
			if err != nil {
				t.Fatal(err)
			}
			defer cs.Close()

			// Check that the client received the expected capabilities.
			initResult := cs.InitializeResult()
			if initResult == nil {
				t.Fatal("InitializeResult is nil")
			}

			if diff := cmp.Diff(tc.wantCapabilities, initResult.Capabilities); diff != "" {
				t.Errorf("Capabilities mismatch (-want +got):\n%s", diff)
			}
		})
	}
}