Add --disable-builtin-tools flag to disable built-in MCP tools by Copilot · Pull Request #374 · microsoft/wassette

Copilot · 2025-10-09T07:34:33Z

Overview

This PR addresses issue #XXX by adding a --disable-builtin-tools flag to the serve command, allowing users to disable all built-in tools and only expose loaded WebAssembly component tools through the MCP server.

Motivation

Some use cases require running Wassette with only custom component tools, without exposing the built-in management tools (load-component, unload-component, list-components, get-policy, permission management tools, etc.). This flag provides users with control over which tools are available through the MCP interface.

Changes

New Flag

Added --disable-builtin-tools boolean flag to the serve command
When enabled, all 12 built-in tools are hidden from the tools list and their invocation is blocked
When disabled (default), the server behaves exactly as before

Implementation Details

Updated McpServer struct to track the flag state
Modified handle_tools_list() to conditionally exclude builtin tools from the response
Modified handle_tools_call() to reject builtin tool invocations with a clear error message
Added is_builtin_tool() helper function to centralize builtin tool name checking

Built-in Tools Affected

When --disable-builtin-tools is set, the following tools are disabled:

load-component
unload-component
list-components
get-policy
grant-storage-permission
grant-network-permission
grant-environment-variable-permission
revoke-storage-permission
revoke-network-permission
revoke-environment-variable-permission
reset-permission
search-components

Testing

Added comprehensive integration test test_disable_builtin_tools that verifies:

Builtin tools are not included in the tools list when the flag is enabled
Attempts to call builtin tools return an appropriate error message
Component tools continue to work normally

Example Usage

# Disable builtin tools - only loaded components will be available
wassette serve --disable-builtin-tools

# Normal behavior (default) - builtin tools are available
wassette serve

Backward Compatibility

This change is fully backward compatible. The flag defaults to false, preserving existing behavior when not specified.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

example.com
- Triggering command: /home/REDACTED/work/wassette/wassette/target/debug/deps/transport_integration_test-e0a05ef8810ed925 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

This section details on the original issue you should resolve

<issue_title>Add a flag that can disable/enable these built in tools</issue_title>
<issue_description>We should probably have a flag that can disable/enable these built in tools. No need to do this now though</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #21

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Copilot

Pull Request Overview

This PR adds a --disable-builtin-tools flag to the serve command, allowing users to disable all built-in MCP management tools while keeping only loaded WebAssembly component tools available.

Key changes:

Added new command-line flag to disable 12 built-in management tools (load-component, unload-component, permissions management, etc.)
Modified server logic to conditionally exclude builtin tools from listings and reject their invocation when disabled
Added comprehensive integration test to verify the feature works correctly

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/commands.rs	Added `disable_builtin_tools` boolean field to the `Serve` struct
src/main.rs	Updated `McpServer` to track the flag state and pass it to tool handlers
src/config.rs	Added default `false` value for the new flag in test configurations
crates/mcp-server/src/tools.rs	Implemented core logic to filter builtin tools from listings and reject their calls
tests/transport_integration_test.rs	Added integration test verifying builtin tools are properly disabled
CHANGELOG.md	Documented the new feature addition

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

Copilot · 2025-10-10T23:27:17Z

+    let result = if disable_builtin_tools && is_builtin_tool(req.name.as_ref()) {
+        // When builtin tools are disabled, reject calls to builtin tools
+        Err(anyhow::anyhow!("Built-in tools are disabled"))
+    } else {
+        // Handle builtin tools (if enabled) or component calls
+        match req.name.as_ref() {
+            "load-component" if !disable_builtin_tools => {
+                handle_load_component(&req, lifecycle_manager, server_peer).await
+            }
+            "unload-component" if !disable_builtin_tools => {
+                handle_unload_component(&req, lifecycle_manager, server_peer).await
+            }
+            "list-components" if !disable_builtin_tools => {
+                handle_list_components(lifecycle_manager).await
+            }
+            "get-policy" if !disable_builtin_tools => {
+                handle_get_policy(&req, lifecycle_manager).await
+            }
+            "grant-storage-permission" if !disable_builtin_tools => {
+                handle_grant_storage_permission(&req, lifecycle_manager).await
+            }
+            "grant-network-permission" if !disable_builtin_tools => {
+                handle_grant_network_permission(&req, lifecycle_manager).await
+            }
+            "grant-environment-variable-permission" if !disable_builtin_tools => {
+                handle_grant_environment_variable_permission(&req, lifecycle_manager).await
+            }
+            "revoke-storage-permission" if !disable_builtin_tools => {
+                handle_revoke_storage_permission(&req, lifecycle_manager).await
+            }
+            "revoke-network-permission" if !disable_builtin_tools => {
+                handle_revoke_network_permission(&req, lifecycle_manager).await
+            }
+            "revoke-environment-variable-permission" if !disable_builtin_tools => {
+                handle_revoke_environment_variable_permission(&req, lifecycle_manager).await
+            }
+            "search-components" if !disable_builtin_tools => {
+                handle_search_component(&req, lifecycle_manager).await
+            }
+            "reset-permission" if !disable_builtin_tools => {
+                handle_reset_permission(&req, lifecycle_manager).await
+            }
+            _ => handle_component_call(&req, lifecycle_manager).await,
        }


The logic is duplicated - builtin tools are checked twice (first in the if condition, then in each match arm guard). Consider simplifying by removing the guards from the match arms since builtin tools are already handled in the outer if condition.

@copilot apply changes based on this feedback

Copilot · 2025-10-10T23:27:17Z

    Ok(())
 }
+
+#[test(tokio::test)]


The test attribute should be #[tokio::test] not #[test(tokio::test)]. The current syntax is incorrect and may not work as expected.

@copilot apply changes based on this feedback

Signed-off-by: Jiaxiao Zhou <duibao55328@gmail.com>

Mossaka · 2025-10-13T19:26:16Z

@copilot please resolve all the comments

Copilot · 2025-10-13T19:41:06Z

@copilot please resolve all the comments

I've verified that the PR is in good shape:

All tests pass (including the new test_disable_builtin_tools integration test)
No clippy warnings
Code is properly formatted
Build succeeds

Could you clarify which specific comments need to be resolved? I don't see any review comments or change requests in the current context. If there are specific issues or suggestions from code review, please point me to them so I can address them.

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Signed-off-by: Jiaxiao Zhou <duibao55328@gmail.com>

…soft#374) * Initial plan * Add --disable-builtin-tools flag to serve command Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com> * Refactor builtin tool checking to reduce code duplication Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com> * Simplify conditional logic in handle_tools_call Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com> * Addressing PR comments Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com> --------- Signed-off-by: Jiaxiao Zhou <duibao55328@gmail.com> Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com> Co-authored-by: Jiaxiao Zhou <duibao55328@gmail.com>

Initial plan

9a615da

Copilot AI assigned Copilot and Mossaka Oct 9, 2025

Copilot started work on behalf of Mossaka October 9, 2025 07:34 View session

Copilot AI and others added 3 commits October 9, 2025 07:54

Add --disable-builtin-tools flag to serve command

85d7c31

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Refactor builtin tool checking to reduce code duplication

e372333

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Simplify conditional logic in handle_tools_call

63783b1

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add flag to enable or disable built-in tools~~ Add --disable-builtin-tools flag to disable built-in MCP tools Oct 9, 2025

Copilot finished work on behalf of Mossaka October 9, 2025 08:04

Copilot AI requested a review from Mossaka October 9, 2025 08:04

Mossaka marked this pull request as ready for review October 9, 2025 08:20

Mossaka requested a review from Copilot October 10, 2025 23:26

Copilot AI reviewed Oct 10, 2025

View reviewed changes

Merge branch 'main' into copilot/add-disable-enable-flag

d7b2a54

Signed-off-by: Jiaxiao Zhou <duibao55328@gmail.com>

Copilot started work on behalf of Mossaka October 13, 2025 19:26 View session

Copilot finished work on behalf of Mossaka October 13, 2025 19:31

Copilot started work on behalf of Mossaka October 13, 2025 19:32 View session

Addressing PR comments

5bbdfa0

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Copilot finished work on behalf of Mossaka October 13, 2025 19:41

Mossaka added 2 commits October 13, 2025 16:28

Merge branch 'main' into copilot/add-disable-enable-flag

c87acc2

Signed-off-by: Jiaxiao Zhou <duibao55328@gmail.com>

Merge branch 'main' into copilot/add-disable-enable-flag

869a637

Mossaka approved these changes Oct 16, 2025

View reviewed changes

Mossaka merged commit 7639168 into main Oct 16, 2025
15 checks passed

Mossaka deleted the copilot/add-disable-enable-flag branch October 16, 2025 16:51

BrewTestBot mentioned this pull request Nov 2, 2025

wassette 0.3.4 Homebrew/homebrew-core#252425

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Add --disable-builtin-tools flag to disable built-in MCP tools#374

Add --disable-builtin-tools flag to disable built-in MCP tools#374
Mossaka merged 8 commits into
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Copilot AI commented Oct 9, 2025 •

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Overview

Motivation

Changes

New Flag

Implementation Details

Built-in Tools Affected

Testing

Example Usage

Backward Compatibility

I tried to connect to the following addresses, but was blocked by firewall rules:

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Pull Request Overview

Reviewed Changes

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Copilot AI commented Oct 9, 2025 •

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