feat: add READ_ONLY mode to disable write tools

README.md

@@ -255,6 +255,7 @@ Without `MCP_AUTH_TOKEN`, the server runs without authentication — suitable fo
 | `DATA_DIR` | Optional | `~/.obsidian-mcp` | Directory for persisted data (metadata index, auth tokens) |
 | `LOG_LEVEL` | Optional | — | Set to `debug` for verbose logging (library logs, change feed, index sync) |
 | `MCP_REFRESH_DAYS` | Optional | `14` | Days before auth session expires |
+| `READ_ONLY` | Optional | `false` | Set to `true` to disable all write tools (`write_note`, `edit_note`, `delete_note`, `move_note`). Only read tools are exposed via MCP. Useful when sharing the server with multiple AI clients and write access should be opt-in. |
 
 Set `VAULT_PATH` for filesystem mode or `COUCHDB_URL` for CouchDB mode.
 

src/main.ts

@@ -32,6 +32,7 @@ const VAULT_NAME = process.env.VAULT_NAME ?? "MyVault";
 const PORT = parseInt(process.env.PORT ?? "8787");
 const BASE_URL = process.env.BASE_URL ?? `http://localhost:${PORT}`;
 const AUTH_TOKEN = process.env.MCP_AUTH_TOKEN;
+const READ_ONLY = process.env.READ_ONLY === "true";
 
 // --- Initialize vault (local or remote) ---
 import type { VaultBackend } from "./vault-backend.js";
@@ -239,7 +240,7 @@ if (AUTH_TOKEN) {
 }
 
 // --- Tools ---
-registerTools(server, vault, searchIndex, VAULT_NAME);
+registerTools(server, vault, searchIndex, VAULT_NAME, READ_ONLY);
 
 // --- Graceful shutdown ---
 async function shutdown() {

src/tools.ts

@@ -6,12 +6,18 @@ import type { SearchIndex } from "./search.js";
 
 const debugLogging = process.env.LOG_LEVEL === "debug";
 
+const WRITE_TOOLS = ["write_note", "edit_note", "delete_note", "move_note"] as const;
+
 export function registerTools(
     server: FastMCP,
     vault: VaultBackend,
     searchIndex: SearchIndex,
     vaultName: string,
+    readOnly = false,
 ) {
+    if (readOnly) {
+        console.log(`READ_ONLY mode: write tools disabled (${WRITE_TOOLS.join(", ")}).`);
+    }
     const _addTool = server.addTool.bind(server);
     server.addTool = (tool: any) => {
         const original = tool.execute;
@@ -41,7 +47,7 @@ export function registerTools(
         },
     });
 
-    server.addTool({
+    if (!readOnly) server.addTool({
         name: "write_note",
         description:
             "Write or update a note in the Obsidian vault. Creates the note if it doesn't exist. Replaces the entire content if it does — read first if you need to preserve existing content.",
@@ -178,7 +184,7 @@ export function registerTools(
 
 
 
-    server.addTool({
+    if (!readOnly) server.addTool({
         name: "edit_note",
         description:
             "Edit a note without rewriting it. Use 'append' (default) to add content to the end, 'prepend' to add after frontmatter, or 'replace' to swap old_text with new content. For replace, the old_text must match exactly once.",
@@ -239,7 +245,7 @@ export function registerTools(
         },
     });
 
-    server.addTool({
+    if (!readOnly) server.addTool({
         name: "delete_note",
         description: "Delete a note from the Obsidian vault.",
         parameters: z.object({
@@ -252,7 +258,7 @@ export function registerTools(
         },
     });
 
-    server.addTool({
+    if (!readOnly) server.addTool({
         name: "move_note",
         description:
             "Move or rename a note. Use this to rename a note within the same folder, move it to a different folder, or both at once. Creates destination folders automatically.",

test/e2e.test.ts

@@ -243,6 +243,27 @@ describe("E2E: delete_note", () => {
 
 // --- Restart Test ---
 
+describe("E2E: READ_ONLY mode", () => {
+    it("hides write tools and rejects write calls when READ_ONLY=true", async () => {
+        await stopServer();
+        await startServer({ VAULT_PATH: vaultDir, VAULT_NAME: "TestVault", READ_ONLY: "true" });
+        assert.ok(serverLogs.includes("READ_ONLY mode"), "should log READ_ONLY mode at startup");
+
+        const list = await mcpCall("tools/list", {});
+        const tools: string[] = (list?.result?.tools ?? []).map((t: any) => t.name);
+        for (const w of ["write_note", "edit_note", "delete_note", "move_note"]) {
+            assert.ok(!tools.includes(w), `${w} should not be registered in READ_ONLY mode`);
+        }
+        for (const r of ["read_note", "list_notes", "list_folders", "list_tags", "get_note_metadata"]) {
+            assert.ok(tools.includes(r), `${r} should remain available in READ_ONLY mode`);
+        }
+
+        const resp = await mcpCall("tools/call", { name: "write_note", arguments: { path: "blocked.md", content: "x" } });
+        assert.ok(resp?.error, "write_note call should return an error");
+        assert.ok(!existsSync(join(vaultDir, "blocked.md")), "no file should be created when write is blocked");
+    });
+});
+
 describe("E2E: cold restart with persisted index", () => {
     it("picks up changes and removes stale entries after restart", async () => {
         // Stop server (triggers saveToDisk)