diff --git a/CLAUDE.md b/CLAUDE.md
index fa05f2b..9124d2b 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -232,13 +232,46 @@ A tool is just an app that is displayed in a tab and an iframe on each app's pag
 
 ### Minimal Tool Structure
 
-A tool needs three files at minimum:
+A tool needs four files at minimum:
 
 **.npmrc**
 ```
 registry=https://npm.nose.space
 ```
 
+**tsconfig.json**
+```json
+{
+  "compilerOptions": {
+    "lib": ["ESNext"],
+    "target": "ESNext",
+    "module": "Preserve",
+    "moduleDetection": "force",
+    "jsx": "react-jsx",
+    "jsxImportSource": "hono/jsx",
+    "allowJs": true,
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "noEmit": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitOverride": true,
+    "noUnusedLocals": false,
+    "noUnusedParameters": false,
+    "noPropertyAccessFromIndexSignature": false,
+    "baseUrl": ".",
+    "paths": {
+      "$*": ["src/server/*"],
+      "#*": ["src/client/*"],
+      "@*": ["src/shared/*"]
+    }
+  }
+}
+```
+
 **package.json**
 ```json
 {
@@ -516,12 +549,13 @@ watch(APPS_DIR, { recursive: true }, (_event, filename) => {
 ### Checklist for New Tools
 
 1. [ ] `.npmrc` contains `registry=https://npm.nose.space`
-2. [ ] `package.json` has `toes.tool: true` and `toes.icon`
-3. [ ] `scripts.toes` uses `bun run --watch index.tsx`
-4. [ ] Dependencies include `@because/forge`, `@because/hype`, `@because/toes`
-5. [ ] Import `baseStyles`, `ToolScript`, `theme` from `@because/toes/tools`
-6. [ ] Layout body includes `<ToolScript />`
-7. [ ] Styles served at `/styles.css` with `baseStyles + stylesToCSS()`
-8. [ ] Main route handles missing `?app` parameter gracefully
-9. [ ] Uses `APPS_DIR/<app>/current` for file paths
-10. [ ] Exports `app.defaults` as default export
+2. [ ] `tsconfig.json` matches the exact config shown above (do not improvise)
+3. [ ] `package.json` has `toes.tool: true` and `toes.icon`
+4. [ ] `scripts.toes` uses `bun run --watch index.tsx`
+5. [ ] Dependencies include `@because/forge`, `@because/hype`, `@because/toes`
+6. [ ] Import `baseStyles`, `ToolScript`, `theme` from `@because/toes/tools`
+7. [ ] Layout body includes `<ToolScript />`
+8. [ ] Styles served at `/styles.css` with `baseStyles + stylesToCSS()`
+9. [ ] Main route handles missing `?app` parameter gracefully
+10. [ ] Uses `APPS_DIR/<app>/current` for file paths
+11. [ ] Exports `app.defaults` as default export