diff --git a/src/filesystem/README.md b/src/filesystem/README.md
index 973f76ef66..91d217af2b 100644
--- a/src/filesystem/README.md
+++ b/src/filesystem/README.md
@@ -175,6 +175,35 @@ The server's directory access control follows this flow:
   - Returns:
     - Directories that this server can read/write from
 
+### Tool annotations (MCP hints)
+
+This server sets [MCP ToolAnnotations](https://modelcontextprotocol.io/specification/2025-03-26/server/tools#toolannotations)
+on each tool so clients can:
+
+- Distinguish **read‑only** tools from write‑capable tools.
+- Understand which write operations are **idempotent** (safe to retry with the same arguments).
+- Highlight operations that may be **destructive** (overwriting or heavily mutating data).
+
+The mapping for filesystem tools is:
+
+| Tool                        | readOnlyHint | idempotentHint | destructiveHint | Notes                                            |
+|-----------------------------|--------------|----------------|-----------------|--------------------------------------------------|
+| `read_text_file`            | `true`       | –              | –               | Pure read                                       |
+| `read_media_file`           | `true`       | –              | –               | Pure read                                       |
+| `read_multiple_files`       | `true`       | –              | –               | Pure read                                       |
+| `list_directory`            | `true`       | –              | –               | Pure read                                       |
+| `list_directory_with_sizes` | `true`       | –              | –               | Pure read                                       |
+| `directory_tree`            | `true`       | –              | –               | Pure read                                       |
+| `search_files`              | `true`       | –              | –               | Pure read                                       |
+| `get_file_info`             | `true`       | –              | –               | Pure read                                       |
+| `list_allowed_directories`  | `true`       | –              | –               | Pure read                                       |
+| `create_directory`          | `false`      | `true`         | `false`         | Re‑creating the same dir is a no‑op             |
+| `write_file`                | `false`      | `true`         | `true`          | Overwrites existing files                       |
+| `edit_file`                 | `false`      | `false`        | `true`          | Re‑applying edits can fail or double‑apply      |
+| `move_file`                 | `false`      | `false`        | `false`         | Move/rename only; repeat usually errors         |
+
+> Note: `idempotentHint` and `destructiveHint` are meaningful only when `readOnlyHint` is `false`, as defined by the MCP spec.
+
 ## Usage with Claude Desktop
 Add this to your `claude_desktop_config.json`:
 
diff --git a/src/filesystem/index.ts b/src/filesystem/index.ts
index 4f521aa58f..79a7b2fe4c 100644
--- a/src/filesystem/index.ts
+++ b/src/filesystem/index.ts
@@ -197,7 +197,8 @@ server.registerTool(
     title: "Read File (Deprecated)",
     description: "Read the complete contents of a file as text. DEPRECATED: Use read_text_file instead.",
     inputSchema: ReadTextFileArgsSchema.shape,
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   readTextFileHandler
 );
@@ -219,7 +220,8 @@ server.registerTool(
       tail: z.number().optional().describe("If provided, returns only the last N lines of the file"),
       head: z.number().optional().describe("If provided, returns only the first N lines of the file")
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   readTextFileHandler
 );
@@ -240,7 +242,8 @@ server.registerTool(
         data: z.string(),
         mimeType: z.string()
       }))
-    }
+    },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof ReadMediaFileArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -290,7 +293,8 @@ server.registerTool(
         .min(1)
         .describe("Array of file paths to read. Each path must be a string pointing to a valid file within allowed directories.")
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof ReadMultipleFilesArgsSchema>) => {
     const results = await Promise.all(
@@ -325,7 +329,8 @@ server.registerTool(
       path: z.string(),
       content: z.string()
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: false, idempotentHint: true, destructiveHint: true }
   },
   async (args: z.infer<typeof WriteFileArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -354,7 +359,8 @@ server.registerTool(
       })),
       dryRun: z.boolean().default(false).describe("Preview changes using git-style diff format")
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: false, idempotentHint: false, destructiveHint: true }
   },
   async (args: z.infer<typeof EditFileArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -378,7 +384,8 @@ server.registerTool(
     inputSchema: {
       path: z.string()
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: false, idempotentHint: true, destructiveHint: false }
   },
   async (args: z.infer<typeof CreateDirectoryArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -403,7 +410,8 @@ server.registerTool(
     inputSchema: {
       path: z.string()
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof ListDirectoryArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -431,7 +439,8 @@ server.registerTool(
       path: z.string(),
       sortBy: z.enum(["name", "size"]).optional().default("name").describe("Sort entries by name or size")
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof ListDirectoryWithSizesArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -509,7 +518,8 @@ server.registerTool(
       path: z.string(),
       excludePatterns: z.array(z.string()).optional().default([])
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof DirectoryTreeArgsSchema>) => {
     interface TreeEntry {
@@ -578,7 +588,8 @@ server.registerTool(
       source: z.string(),
       destination: z.string()
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: false, idempotentHint: false, destructiveHint: false }
   },
   async (args: z.infer<typeof MoveFileArgsSchema>) => {
     const validSourcePath = await validatePath(args.source);
@@ -608,7 +619,8 @@ server.registerTool(
       pattern: z.string(),
       excludePatterns: z.array(z.string()).optional().default([])
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof SearchFilesArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -633,7 +645,8 @@ server.registerTool(
     inputSchema: {
       path: z.string()
     },
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async (args: z.infer<typeof GetFileInfoArgsSchema>) => {
     const validPath = await validatePath(args.path);
@@ -658,7 +671,8 @@ server.registerTool(
       "Use this to understand which directories and their nested paths are available " +
       "before trying to access files.",
     inputSchema: {},
-    outputSchema: { content: z.string() }
+    outputSchema: { content: z.string() },
+    annotations: { readOnlyHint: true }
   },
   async () => {
     const text = `Allowed directories:\n${allowedDirectories.join('\n')}`;