diff --git a/src/cmdforge/cli/__init__.py b/src/cmdforge/cli/__init__.py
index 8a50847..5b5d393 100644
--- a/src/cmdforge/cli/__init__.py
+++ b/src/cmdforge/cli/__init__.py
@@ -190,6 +190,12 @@ def main():
     p_reg_publish.add_argument("--owner", default="", help="Owner override (admin only, e.g. 'official')")
     p_reg_publish.set_defaults(func=cmd_registry)
 
+    # registry update-readme
+    p_reg_update_readme = registry_sub.add_parser("update-readme", help="Update README for a published tool")
+    p_reg_update_readme.add_argument("tool", help="Tool name (local name, will resolve owner)")
+    p_reg_update_readme.add_argument("--all", action="store_true", dest="update_all", help="Update README for all published tools that have a local README.md")
+    p_reg_update_readme.set_defaults(func=cmd_registry)
+
     # registry my-tools
     p_reg_mytools = registry_sub.add_parser("my-tools", help="List your published tools")
     p_reg_mytools.set_defaults(func=cmd_registry)
diff --git a/src/cmdforge/cli/registry_commands.py b/src/cmdforge/cli/registry_commands.py
index 63459a1..0feb048 100644
--- a/src/cmdforge/cli/registry_commands.py
+++ b/src/cmdforge/cli/registry_commands.py
@@ -29,6 +29,8 @@ def cmd_registry(args):
         return _cmd_registry_update(args)
     elif args.registry_cmd == "publish":
         return _cmd_registry_publish(args)
+    elif args.registry_cmd == "update-readme":
+        return _cmd_registry_update_readme(args)
     elif args.registry_cmd == "my-tools":
         return _cmd_registry_my_tools(args)
     elif args.registry_cmd == "status":
@@ -47,6 +49,7 @@ def cmd_registry(args):
         print("  info <tool>        Show tool information")
         print("  update             Update local index cache")
         print("  publish [path]     Publish a tool")
+        print("  update-readme      Update README for published tool(s)")
         print("  my-tools           List your published tools")
         print("  status <tool>      Check moderation status of a tool")
         print("  browse             Browse tools (GUI)")
@@ -635,6 +638,86 @@ def _cmd_registry_publish(args):
     return 0
 
 
+def _cmd_registry_update_readme(args):
+    """Update README for published tool(s) on the registry."""
+    from ..registry_client import RegistryError, get_client
+    from ..tool import TOOLS_DIR, list_tools
+
+    try:
+        client = get_client()
+    except RegistryError as e:
+        print(f"Error: {e}", file=sys.stderr)
+        return 1
+
+    if getattr(args, "update_all", False):
+        # Update all published tools that have a local README
+        tools = list_tools()
+        updated = 0
+        skipped = 0
+        failed = 0
+        for tool_name in tools:
+            tool_dir = TOOLS_DIR / tool_name
+            config_path = tool_dir / "config.yaml"
+            readme_path = tool_dir / "README.md"
+
+            if not readme_path.exists():
+                continue
+
+            # Check if published
+            try:
+                config = yaml.safe_load(config_path.read_text()) or {}
+            except Exception:
+                continue
+            owner = config.get("registry_owner", "")
+            if not owner:
+                skipped += 1
+                continue
+
+            readme_content = readme_path.read_text()
+            try:
+                result = client.update_readme(owner, tool_name, readme_content)
+                count = result.get("versions_updated", 0)
+                print(f"  {owner}/{tool_name}: updated ({count} version(s))")
+                updated += 1
+            except RegistryError as e:
+                print(f"  {owner}/{tool_name}: FAILED - {e}", file=sys.stderr)
+                failed += 1
+
+        print(f"\nDone: {updated} updated, {failed} failed, {skipped} skipped (not published)")
+        return 0
+
+    # Single tool mode
+    tool_name = args.tool
+    tool_dir = TOOLS_DIR / tool_name
+    config_path = tool_dir / "config.yaml"
+    readme_path = tool_dir / "README.md"
+
+    if not config_path.exists():
+        print(f"Error: Tool '{tool_name}' not found", file=sys.stderr)
+        return 1
+
+    if not readme_path.exists():
+        print(f"Error: No README.md found for '{tool_name}'", file=sys.stderr)
+        return 1
+
+    config = yaml.safe_load(config_path.read_text()) or {}
+    owner = config.get("registry_owner", "")
+    if not owner:
+        print(f"Error: Tool '{tool_name}' has no registry_owner — not published?", file=sys.stderr)
+        return 1
+
+    readme_content = readme_path.read_text()
+    try:
+        result = client.update_readme(owner, tool_name, readme_content)
+        count = result.get("versions_updated", 0)
+        print(f"Updated README for {owner}/{tool_name} ({count} version(s))")
+    except RegistryError as e:
+        print(f"Error: {e}", file=sys.stderr)
+        return 1
+
+    return 0
+
+
 def _cmd_registry_my_tools(args):
     """List your published tools."""
     from ..registry_client import RegistryError, get_client
diff --git a/src/cmdforge/registry/app.py b/src/cmdforge/registry/app.py
index 64cce2c..ce1402d 100644
--- a/src/cmdforge/registry/app.py
+++ b/src/cmdforge/registry/app.py
@@ -2815,6 +2815,36 @@ def create_app() -> Flask:
 
         return jsonify({"data": {"status": "active", "owner": owner, "name": name}})
 
+    @app.route("/api/v1/tools/<owner>/<name>/readme", methods=["PATCH"])
+    @require_token
+    def update_tool_readme(owner: str, name: str) -> Response:
+        """Update the README for an existing tool without affecting config or hash."""
+        if g.current_publisher["slug"] != owner:
+            return error_response("FORBIDDEN", "You can only update your own tools", 403)
+
+        data = request.get_json() or {}
+        readme = data.get("readme")
+        if readme is None:
+            return error_response("VALIDATION_ERROR", "Missing 'readme' field", 400)
+
+        version = data.get("version")
+        if version:
+            result = g.db.execute(
+                "UPDATE tools SET readme = ? WHERE owner = ? AND name = ? AND version = ?",
+                [readme, owner, name, version],
+            )
+        else:
+            # Update all versions
+            result = g.db.execute(
+                "UPDATE tools SET readme = ? WHERE owner = ? AND name = ?",
+                [readme, owner, name],
+            )
+        if result.rowcount == 0:
+            return error_response("TOOL_NOT_FOUND", f"Tool {owner}/{name} not found", 404)
+        g.db.commit()
+
+        return jsonify({"data": {"status": "updated", "owner": owner, "name": name, "versions_updated": result.rowcount}})
+
     @app.route("/api/v1/me/settings", methods=["PUT"])
     @require_token
     def update_settings() -> Response:
diff --git a/src/cmdforge/registry_client.py b/src/cmdforge/registry_client.py
index 87e183d..78106eb 100644
--- a/src/cmdforge/registry_client.py
+++ b/src/cmdforge/registry_client.py
@@ -666,6 +666,35 @@ class RegistryClient:
 
         return response.json().get("data", {})
 
+    def update_readme(self, owner: str, name: str, readme: str, version: str = "") -> Dict[str, Any]:
+        """
+        Update the README for an existing published tool.
+
+        Args:
+            owner: Tool owner slug
+            name: Tool name
+            readme: New README content
+            version: Optional specific version to update (default: all versions)
+
+        Returns:
+            Dict with update status
+        """
+        payload: Dict[str, Any] = {"readme": readme}
+        if version:
+            payload["version"] = version
+
+        response = self._request(
+            "PATCH",
+            f"/tools/{owner}/{name}/readme",
+            json_data=payload,
+            require_auth=True,
+        )
+
+        if response.status_code not in (200, 201):
+            self._handle_error_response(response)
+
+        return response.json().get("data", {})
+
     def validate_token(self) -> tuple[bool, str]:
         """
         Validate that the current token is valid.