diff --git a/packages/core/src/adapters/mcp.ts b/packages/core/src/adapters/mcp.ts
index 8c5130b8..13396196 100644
--- a/packages/core/src/adapters/mcp.ts
+++ b/packages/core/src/adapters/mcp.ts
@@ -5,10 +5,10 @@
  * Uses camelCase naming and _meta.ui.* namespace.
  */
 
-import type { ToolDef, ToolAnnotations } from "../types/tools";
+import type { ToolDef } from "../types/tools";
 import type { UIDef } from "../types/ui";
 import type { ProtocolAdapter, ToolMetaResult, UIResourceMetaResult } from "./types";
-import { mapVisibilityToMcp } from "../utils/metadata";
+import { mapVisibilityToMcp, buildAnnotations } from "../utils/metadata";
 import { generateMcpCSPMetadata } from "../utils/csp";
 
 // =============================================================================
@@ -37,7 +37,7 @@ export class McpAdapter implements ProtocolAdapter {
     };
 
     // Build annotations if specified
-    const annotations = this.buildAnnotations(toolDef.annotations);
+    const annotations = buildAnnotations(toolDef.annotations);
 
     // Compatibility notes:
     // - ext-apps / MCP Apps reference shape commonly uses nested `_meta.ui.resourceUri`.
@@ -55,32 +55,6 @@ export class McpAdapter implements ProtocolAdapter {
     };
   }
 
-  /**
-   * Build MCP annotations from tool annotations
-   */
-  private buildAnnotations(annotations?: ToolAnnotations): Record<string, unknown> | undefined {
-    if (!annotations) {
-      return undefined;
-    }
-
-    const result: Record<string, unknown> = {};
-
-    if (annotations.readOnlyHint !== undefined) {
-      result.readOnlyHint = annotations.readOnlyHint;
-    }
-    if (annotations.destructiveHint !== undefined) {
-      result.destructiveHint = annotations.destructiveHint;
-    }
-    if (annotations.openWorldHint !== undefined) {
-      result.openWorldHint = annotations.openWorldHint;
-    }
-    if (annotations.idempotentHint !== undefined) {
-      result.idempotentHint = annotations.idempotentHint;
-    }
-
-    return Object.keys(result).length > 0 ? result : undefined;
-  }
-
   /**
    * Build UI resource metadata for MCP protocol
    */
diff --git a/packages/core/src/adapters/openai.ts b/packages/core/src/adapters/openai.ts
index bddf7e68..f6b88e2b 100644
--- a/packages/core/src/adapters/openai.ts
+++ b/packages/core/src/adapters/openai.ts
@@ -5,10 +5,10 @@
  * Uses snake_case naming and openai/* prefixed keys.
  */
 
-import type { ToolDef, ToolAnnotations } from "../types/tools";
+import type { ToolDef } from "../types/tools";
 import type { UIDef } from "../types/ui";
 import type { ProtocolAdapter, ToolMetaResult, UIResourceMetaResult } from "./types";
-import { mapVisibilityToOpenAI } from "../utils/metadata";
+import { mapVisibilityToOpenAI, buildAnnotations } from "../utils/metadata";
 import { generateOpenAICSPMetadata } from "../utils/csp";
 
 // =============================================================================
@@ -60,7 +60,7 @@ export class OpenAIAdapter implements ProtocolAdapter {
     }
 
     // Build annotations if specified
-    const annotations = this.buildAnnotations(toolDef.annotations);
+    const annotations = buildAnnotations(toolDef.annotations);
 
     return {
       annotations,
@@ -68,34 +68,6 @@ export class OpenAIAdapter implements ProtocolAdapter {
     };
   }
 
-  /**
-   * Build OpenAI annotations from tool annotations
-   *
-   * OpenAI uses the same annotation names as MCP spec
-   */
-  private buildAnnotations(annotations?: ToolAnnotations): Record<string, unknown> | undefined {
-    if (!annotations) {
-      return undefined;
-    }
-
-    const result: Record<string, unknown> = {};
-
-    if (annotations.readOnlyHint !== undefined) {
-      result.readOnlyHint = annotations.readOnlyHint;
-    }
-    if (annotations.destructiveHint !== undefined) {
-      result.destructiveHint = annotations.destructiveHint;
-    }
-    if (annotations.openWorldHint !== undefined) {
-      result.openWorldHint = annotations.openWorldHint;
-    }
-    if (annotations.idempotentHint !== undefined) {
-      result.idempotentHint = annotations.idempotentHint;
-    }
-
-    return Object.keys(result).length > 0 ? result : undefined;
-  }
-
   /**
    * Build UI resource metadata for OpenAI protocol
    */
diff --git a/packages/core/src/events/types.ts b/packages/core/src/events/types.ts
index 1b38be54..614dd029 100644
--- a/packages/core/src/events/types.ts
+++ b/packages/core/src/events/types.ts
@@ -4,7 +4,7 @@
  * @module events/types
  */
 
-import type { ToolContext, ToolDefs as _ToolDefs } from "../types/tools";
+import type { ToolContext } from "../types/tools";
 import type { AppConfig } from "../types/config";
 
 // =============================================================================
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 617840f0..4a5d9eda 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -151,6 +151,7 @@ export type { ErrorCodeType } from "./utils/errors";
 export {
   mapVisibilityToMcp,
   mapVisibilityToOpenAI,
+  buildAnnotations,
   generateToolMetadata,
   generateAllToolsMetadata,
 } from "./utils/metadata";
diff --git a/packages/core/src/plugins/builtin/logging.ts b/packages/core/src/plugins/builtin/logging.ts
index 448da0c4..11569e95 100644
--- a/packages/core/src/plugins/builtin/logging.ts
+++ b/packages/core/src/plugins/builtin/logging.ts
@@ -16,6 +16,7 @@
 import { z } from "zod";
 import { createPlugin } from "../types";
 import type { ToolCallContext, PluginInitContext, PluginStartContext } from "../types";
+import { safeStringify } from "../../debug/logger";
 
 /**
  * Log level enumeration
@@ -59,37 +60,6 @@ function timestamp(): string {
   return new Date().toISOString();
 }
 
-/**
- * Safely stringify objects, handling circular references
- */
-function safeStringify(obj: unknown): string {
-  try {
-    return JSON.stringify(obj, null, 2);
-  } catch {
-    try {
-      return JSON.stringify(obj, getCircularReplacer(), 2);
-    } catch {
-      return String(obj);
-    }
-  }
-}
-
-/**
- * JSON replacer function that handles circular references
- */
-function getCircularReplacer() {
-  const seen = new WeakSet();
-  return (_key: string, value: unknown): unknown => {
-    if (typeof value === "object" && value !== null) {
-      if (seen.has(value)) {
-        return "[Circular]";
-      }
-      seen.add(value);
-    }
-    return value;
-  };
-}
-
 /**
  * Built-in logging plugin
  *
diff --git a/packages/core/src/utils/csp.ts b/packages/core/src/utils/csp.ts
index 218f796f..fccfe7c1 100644
--- a/packages/core/src/utils/csp.ts
+++ b/packages/core/src/utils/csp.ts
@@ -8,7 +8,7 @@
  * @module utils/csp
  */
 
-import type { CSPConfig } from "../types/ui";
+import type { CSPConfig, UIDef } from "../types/ui";
 
 // =============================================================================
 // MCP CSP METADATA
@@ -105,8 +105,6 @@ export function generateOpenAICSPMetadata(csp: CSPConfig): OpenAICSPMetadata {
 // UI RESOURCE METADATA GENERATION
 // =============================================================================
 
-import type { UIDef } from "../types/ui";
-
 /**
  * MCP UI resource metadata format
  *
diff --git a/packages/core/src/utils/metadata.ts b/packages/core/src/utils/metadata.ts
index 7a6c3087..f4c36a94 100644
--- a/packages/core/src/utils/metadata.ts
+++ b/packages/core/src/utils/metadata.ts
@@ -8,7 +8,7 @@
  * @module utils/metadata
  */
 
-import type { ToolDef, Visibility } from "../types/tools";
+import type { ToolDef, Visibility, ToolAnnotations } from "../types/tools";
 import { zodToJsonSchema } from "./schema";
 
 // =============================================================================
@@ -102,6 +102,46 @@ export function mapVisibilityToOpenAI(visibility?: Visibility): OpenAIVisibility
   }
 }
 
+// =============================================================================
+// TOOL ANNOTATIONS
+// =============================================================================
+
+/**
+ * Build protocol-agnostic annotations from tool annotations.
+ *
+ * Both MCP and OpenAI use the same annotation property names,
+ * so this function is shared between adapters.
+ *
+ * @param annotations - Tool annotations from tool definition
+ * @returns Record of annotation properties, or undefined if no annotations
+ *
+ * @internal
+ */
+export function buildAnnotations(
+  annotations?: ToolAnnotations
+): Record<string, unknown> | undefined {
+  if (!annotations) {
+    return undefined;
+  }
+
+  const result: Record<string, unknown> = {};
+
+  if (annotations.readOnlyHint !== undefined) {
+    result.readOnlyHint = annotations.readOnlyHint;
+  }
+  if (annotations.destructiveHint !== undefined) {
+    result.destructiveHint = annotations.destructiveHint;
+  }
+  if (annotations.openWorldHint !== undefined) {
+    result.openWorldHint = annotations.openWorldHint;
+  }
+  if (annotations.idempotentHint !== undefined) {
+    result.idempotentHint = annotations.idempotentHint;
+  }
+
+  return Object.keys(result).length > 0 ? result : undefined;
+}
+
 // =============================================================================
 // TOOL METADATA GENERATION
 // =============================================================================