Tool search configuration support

dotnet/src/Client.cs

@@ -1088,6 +1088,7 @@ public async Task<CopilotSession> CreateSessionAsync(SessionConfig config, Cance
                 InstructionDirectories: config.InstructionDirectories,
                 PluginDirectories: config.PluginDirectories,
                 LargeOutput: config.LargeOutput,
+                ToolSearch: config.ToolSearch,
                 Memory: config.Memory,
                 Canvases: config.Canvases,
                 RequestCanvasRenderer: config.RequestCanvasRenderer,
@@ -1297,6 +1298,7 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
                 InstructionDirectories: config.InstructionDirectories,
                 PluginDirectories: config.PluginDirectories,
                 LargeOutput: config.LargeOutput,
+                ToolSearch: config.ToolSearch,
                 Memory: config.Memory,
                 Canvases: config.Canvases,
                 RequestCanvasRenderer: config.RequestCanvasRenderer,
@@ -2630,6 +2632,7 @@ internal record CreateSessionRequest(
         IList<string>? InstructionDirectories = null,
         IList<string>? PluginDirectories = null,
         LargeToolOutputConfig? LargeOutput = null,
+        ToolSearchConfig? ToolSearch = null,
         MemoryConfiguration? Memory = null,
 #pragma warning disable GHCP001
         IList<CanvasDeclaration>? Canvases = null,
@@ -2729,6 +2732,7 @@ internal record ResumeSessionRequest(
         IList<string>? InstructionDirectories = null,
         IList<string>? PluginDirectories = null,
         LargeToolOutputConfig? LargeOutput = null,
+        ToolSearchConfig? ToolSearch = null,
         MemoryConfiguration? Memory = null,
 #pragma warning disable GHCP001
         IList<CanvasDeclaration>? Canvases = null,

dotnet/src/Types.cs

@@ -679,6 +679,12 @@ public sealed class ToolResultObject
     [JsonPropertyName("toolTelemetry")]
     public IDictionary<string, object>? ToolTelemetry { get; set; }
 
+    /// <summary>
+    /// Names of tools returned by a tool-search tool.
+    /// </summary>
+    [JsonPropertyName("toolReferences")]
+    public IList<string>? ToolReferences { get; set; }
+
     /// <summary>
     /// Converts the result of an <see cref="AIFunction"/> invocation into a
     /// <see cref="ToolResultObject"/>. Handles <see cref="ToolResultAIContent"/>,
@@ -2703,6 +2709,30 @@ public sealed class LargeToolOutputConfig
     public string? OutputDirectory { get; set; }
 }
 
+/// <summary>
+/// Overrides the runtime's built-in tool-search behavior.
+/// Defers tools to keep the model's active tool set small.
+/// To override the tool-search tool's implementation, register a tool
+/// named "tool_search_tool" with <c>OverridesBuiltInTool</c> set to
+/// <see langword="true"/>.
+/// </summary>
+public sealed class ToolSearchConfig
+{
+    /// <summary>
+    /// Enable or disable tool search.
+    /// </summary>
+    [JsonPropertyName("enabled")]
+    public bool? Enabled { get; set; }
+
+    /// <summary>
+    /// The tool count above which MCP and external tools are deferred behind
+    /// tool search. When <see langword="null"/>, the runtime default (30)
+    /// applies.
+    /// </summary>
+    [JsonPropertyName("deferThreshold")]
+    public int? DeferThreshold { get; set; }
+}
+
 /// <summary>
 /// Configuration for session memory.
 /// </summary>
@@ -2811,6 +2841,7 @@ protected SessionConfigBase(SessionConfigBase? other)
         Hooks = other.Hooks;
         InfiniteSessions = other.InfiniteSessions;
         LargeOutput = other.LargeOutput;
+        ToolSearch = other.ToolSearch;
         Memory = other.Memory;
         McpServers = other.McpServers is not null
             ? (other.McpServers is Dictionary<string, McpServerConfig> dict
@@ -3215,6 +3246,13 @@ protected SessionConfigBase(SessionConfigBase? other)
     /// </summary>
     public LargeToolOutputConfig? LargeOutput { get; set; }
 
+    /// <summary>
+    /// Overrides the runtime's built-in tool-search behavior.
+    /// Tool search defers tools to keep the model's active tool set small. When <see langword="null"/>,
+    /// the runtime default applies.
+    /// </summary>
+    public ToolSearchConfig? ToolSearch { get; set; }
+
     /// <summary>
     /// Configuration for session memory. When set, controls whether the
     /// session can read and write persistent memory.

go/client.go

@@ -722,6 +722,7 @@ func (c *Client) CreateSession(ctx context.Context, config *SessionConfig) (*Ses
 	req.DisabledSkills = config.DisabledSkills
 	req.InfiniteSessions = config.InfiniteSessions
 	req.LargeOutput = config.LargeOutput
+	req.ToolSearch = config.ToolSearch
 	req.Memory = config.Memory
 	req.GitHubToken = config.GitHubToken
 	req.RemoteSession = config.RemoteSession
@@ -1085,6 +1086,7 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 	req.DisabledSkills = config.DisabledSkills
 	req.InfiniteSessions = config.InfiniteSessions
 	req.LargeOutput = config.LargeOutput
+	req.ToolSearch = config.ToolSearch
 	req.Memory = config.Memory
 	req.GitHubToken = config.GitHubToken
 	req.RemoteSession = config.RemoteSession

go/session.go

@@ -1542,6 +1542,7 @@ func (s *Session) executeToolAndRespond(requestID, toolName, toolCallID string,
 		TextResultForLlm: textResultForLLM,
 		ToolTelemetry:    result.ToolTelemetry,
 		ResultType:       &effectiveResultType,
+		ToolReferences:   result.ToolReferences,
 	}
 	if result.Error != "" {
 		rpcResult.Error = &result.Error

go/types.go

@@ -948,6 +948,18 @@ type LargeToolOutputConfig struct {
 	OutputDirectory string `json:"outputDir,omitempty"`
 }
 
+// ToolSearchConfig allows to configure tool search behavior.
+// Tool search defers tools to keep the model's active tool set small.
+// To override the tool-search tool's implementation, register a
+// [Tool] named "tool_search_tool" with OverridesBuiltInTool set to true.
+type ToolSearchConfig struct {
+	// Controls whether tool search is enabled.
+	Enabled *bool `json:"enabled,omitempty"`
+	// DeferThreshold is the tool count above which MCP and external tools are
+	// deferred behind tool search. When nil, the runtime default (30) applies.
+	DeferThreshold *int `json:"deferThreshold,omitempty"`
+}
+
 // SessionFSCapabilities declares optional provider capabilities.
 type SessionFSCapabilities struct {
 	// Sqlite indicates whether the provider supports SQLite query/exists operations.
@@ -1153,6 +1165,10 @@ type SessionConfig struct {
 	// output exceeding the configured size, the output is written to a temp file
 	// and a reference is returned to the model instead of the full payload.
 	LargeOutput *LargeToolOutputConfig
+	// ToolSearch overrides the runtime's built-in tool-search behavior, which
+	// defers rarely used tools behind a searchable index. When nil, the runtime
+	// default applies.
+	ToolSearch *ToolSearchConfig
 	// Memory configures the memory feature for the session. When omitted, the
 	// runtime default applies.
 	Memory *MemoryConfiguration
@@ -1300,6 +1316,8 @@ type ToolResult struct {
 	Error               string             `json:"error,omitempty"`
 	SessionLog          string             `json:"sessionLog,omitempty"`
 	ToolTelemetry       map[string]any     `json:"toolTelemetry,omitempty"`
+	// ToolReferences lists names of tools returned by a tool-search tool.
+	ToolReferences []string `json:"toolReferences,omitempty"`
 }
 
 // CommandContext provides context about a slash-command invocation.
@@ -1596,6 +1614,10 @@ type ResumeSessionConfig struct {
 	// output exceeding the configured size, the output is written to a temp file
 	// and a reference is returned to the model instead of the full payload.
 	LargeOutput *LargeToolOutputConfig
+	// ToolSearch overrides the runtime's built-in tool-search behavior, which
+	// defers rarely used tools behind a searchable index. When nil, the runtime
+	// default applies.
+	ToolSearch *ToolSearchConfig
 	// Memory configures the memory feature for the session. When omitted, the
 	// runtime default applies.
 	Memory *MemoryConfiguration
@@ -2109,6 +2131,7 @@ type createSessionRequest struct {
 	DisabledSkills                     []string                               `json:"disabledSkills,omitempty"`
 	InfiniteSessions                   *InfiniteSessionConfig                 `json:"infiniteSessions,omitempty"`
 	LargeOutput                        *LargeToolOutputConfig                 `json:"largeOutput,omitempty"`
+	ToolSearch                         *ToolSearchConfig                      `json:"toolSearch,omitempty"`
 	Memory                             *MemoryConfiguration                   `json:"memory,omitempty"`
 	Commands                           []wireCommand                          `json:"commands,omitempty"`
 	RequestElicitation                 *bool                                  `json:"requestElicitation,omitempty"`
@@ -2198,6 +2221,7 @@ type resumeSessionRequest struct {
 	DisabledSkills                     []string                               `json:"disabledSkills,omitempty"`
 	InfiniteSessions                   *InfiniteSessionConfig                 `json:"infiniteSessions,omitempty"`
 	LargeOutput                        *LargeToolOutputConfig                 `json:"largeOutput,omitempty"`
+	ToolSearch                         *ToolSearchConfig                      `json:"toolSearch,omitempty"`
 	Memory                             *MemoryConfiguration                   `json:"memory,omitempty"`
 	Commands                           []wireCommand                          `json:"commands,omitempty"`
 	RequestElicitation                 *bool                                  `json:"requestElicitation,omitempty"`

java/src/main/java/com/github/copilot/SessionRequestBuilder.java

@@ -145,6 +145,7 @@ static CreateSessionRequest buildCreateRequest(SessionConfig config, String sess
         request.setInstructionDirectories(config.getInstructionDirectories());
         request.setPluginDirectories(config.getPluginDirectories());
         request.setLargeOutput(config.getLargeOutput());
+        request.setToolSearch(config.getToolSearch());
         request.setMemory(config.getMemory());
         request.setDisabledSkills(config.getDisabledSkills());
         request.setConfigDirectory(config.getConfigDirectory());
@@ -280,6 +281,7 @@ static ResumeSessionRequest buildResumeRequest(String sessionId, ResumeSessionCo
         request.setInstructionDirectories(config.getInstructionDirectories());
         request.setPluginDirectories(config.getPluginDirectories());
         request.setLargeOutput(config.getLargeOutput());
+        request.setToolSearch(config.getToolSearch());
         request.setMemory(config.getMemory());
         request.setDisabledSkills(config.getDisabledSkills());
         request.setInfiniteSessions(config.getInfiniteSessions());

java/src/main/java/com/github/copilot/rpc/CreateSessionRequest.java

@@ -138,6 +138,9 @@ public final class CreateSessionRequest {
     @JsonProperty("largeOutput")
     private LargeToolOutputConfig largeOutput;
 
+    @JsonProperty("toolSearch")
+    private ToolSearchConfig toolSearch;
+
     @JsonProperty("memory")
     private MemoryConfiguration memory;
 
@@ -620,6 +623,16 @@ public void setLargeOutput(LargeToolOutputConfig largeOutput) {
         this.largeOutput = largeOutput;
     }
 
+    /** Gets tool-search config. @return the tool-search config */
+    public ToolSearchConfig getToolSearch() {
+        return toolSearch;
+    }
+
+    /** Sets tool-search config. @param toolSearch the tool-search config */
+    public void setToolSearch(ToolSearchConfig toolSearch) {
+        this.toolSearch = toolSearch;
+    }
+
     /** Gets memory config. @return the memory config */
     public MemoryConfiguration getMemory() {
         return memory;

java/src/main/java/com/github/copilot/rpc/ResumeSessionConfig.java

@@ -90,6 +90,7 @@ public class ResumeSessionConfig {
     private List<String> instructionDirectories;
     private List<String> pluginDirectories;
     private LargeToolOutputConfig largeOutput;
+    private ToolSearchConfig toolSearch;
     private MemoryConfiguration memory;
     private List<String> disabledSkills;
     private InfiniteSessionConfig infiniteSessions;
@@ -1446,6 +1447,27 @@ public ResumeSessionConfig setLargeOutput(LargeToolOutputConfig largeOutput) {
         return this;
     }
 
+    /**
+     * Gets the tool-search configuration.
+     *
+     * @return the tool-search config, or {@code null} for the runtime default
+     */
+    public ToolSearchConfig getToolSearch() {
+        return toolSearch;
+    }
+
+    /**
+     * Sets the tool-search configuration.
+     *
+     * @param toolSearch
+     *            the tool-search config
+     * @return this config for method chaining
+     */
+    public ResumeSessionConfig setToolSearch(ToolSearchConfig toolSearch) {
+        this.toolSearch = toolSearch;
+        return this;
+    }
+
     /**
      * Gets the configuration for session memory.
      *
@@ -1806,6 +1828,7 @@ public ResumeSessionConfig clone() {
                 : null;
         copy.pluginDirectories = this.pluginDirectories != null ? new ArrayList<>(this.pluginDirectories) : null;
         copy.largeOutput = this.largeOutput;
+        copy.toolSearch = this.toolSearch;
         copy.memory = this.memory;
         copy.disabledSkills = this.disabledSkills != null ? new ArrayList<>(this.disabledSkills) : null;
         copy.infiniteSessions = this.infiniteSessions;

java/src/main/java/com/github/copilot/rpc/ResumeSessionRequest.java

@@ -178,6 +178,9 @@ public final class ResumeSessionRequest {
     @JsonProperty("largeOutput")
     private LargeToolOutputConfig largeOutput;
 
+    @JsonProperty("toolSearch")
+    private ToolSearchConfig toolSearch;
+
     @JsonProperty("memory")
     private MemoryConfiguration memory;
 
@@ -836,6 +839,16 @@ public void setLargeOutput(LargeToolOutputConfig largeOutput) {
         this.largeOutput = largeOutput;
     }
 
+    /** Gets tool-search config. @return the tool-search config */
+    public ToolSearchConfig getToolSearch() {
+        return toolSearch;
+    }
+
+    /** Sets tool-search config. @param toolSearch the tool-search config */
+    public void setToolSearch(ToolSearchConfig toolSearch) {
+        this.toolSearch = toolSearch;
+    }
+
     /** Gets memory config. @return the memory config */
     public MemoryConfiguration getMemory() {
         return memory;

java/src/main/java/com/github/copilot/rpc/SessionConfig.java

@@ -80,6 +80,7 @@ public class SessionConfig {
     private List<String> instructionDirectories;
     private List<String> pluginDirectories;
     private LargeToolOutputConfig largeOutput;
+    private ToolSearchConfig toolSearch;
     private MemoryConfiguration memory;
     private List<String> disabledSkills;
     private String configDirectory;
@@ -1129,6 +1130,28 @@ public SessionConfig setLargeOutput(LargeToolOutputConfig largeOutput) {
         return this;
     }
 
+    /**
+     * Gets the tool-search override configuration.
+     *
+     * @return the tool-search config, or {@code null} for the runtime default
+     */
+    public ToolSearchConfig getToolSearch() {
+        return toolSearch;
+    }
+
+    /**
+     * Sets the tool-search override configuration. When {@code null}, the runtime
+     * default tool-search behavior applies.
+     *
+     * @param toolSearch
+     *            the tool-search config
+     * @return this config instance for method chaining
+     */
+    public SessionConfig setToolSearch(ToolSearchConfig toolSearch) {
+        this.toolSearch = toolSearch;
+        return this;
+    }
+
     /**
      * Gets the configuration for session memory.
      *
@@ -1931,6 +1954,7 @@ public SessionConfig clone() {
                 : null;
         copy.pluginDirectories = this.pluginDirectories != null ? new ArrayList<>(this.pluginDirectories) : null;
         copy.largeOutput = this.largeOutput;
+        copy.toolSearch = this.toolSearch;
         copy.memory = this.memory;
         copy.disabledSkills = this.disabledSkills != null ? new ArrayList<>(this.disabledSkills) : null;
         copy.configDirectory = this.configDirectory;