Tool BuilderCAUTION
MCP server that creates its own tools as needed
Overview
From the repository's own README, as read at the audited commit. Badges and raw HTML are left out.
MCP Tool Builder
An MCP server that empowers LLMs to dynamically create new tools through MCP clients such as Claude Desktop.
Features
- Create new tools by describing them in natural language
- Requires client restart to use new tools (Claude Desktop)
- New tools are saved as python scriptlets in ...\\mcp-tool-builder\\tools
- New tool definitions are saved in ...\\mcp-tool-builder\\tools\tools.json
Example tools included at installation
- getbitcoinprice: Fetches current Bitcoin price from CoinGecko
- getweatherforecast: Gets weather for US ZIP codes (uses geopy)
Creating New Tools
Use the create_tool command in Claude Desktop (or suggest strongly!!) to create new tools dynamically
Installation
- Clone this repository
- Install dependencies:
cd mcp-tool-builder uv venv .venv\Scripts\activate uv pip install -e .
Usage with Claude Desktop
Add to claude_desktop_config.json:
{
"mcpServers": {
"tool-builder": {
"command": "uv",
"args": [
"--directory",
"PATH_TO\\mcp-tool-builder",
"run",
"tool-builder"
]
}
}
}a4c39b60da24OBSERVED · 2026-10-09Connect
Built from this server's own package name, version and transport as found in its source — not copied from anyone's documentation, so it cannot drift against a page we do not control.
claude mcp add mcp-tool-builder -- uvx mcp-tool-builder
{
"mcpServers": {
"mcp-tool-builder": {
"command": "uvx",
"args": [
"mcp-tool-builder"
]
}
}
}Exposed tools (2)
1 read · 1 write · 0 destructive.
| Tool | Risk | Description |
|---|---|---|
create_tool | write | Create a new Python tool with specified functionality |
list_available_tools | read | List all currently available tools |
Trust audit
CAUTIONgrade B · trust 88/100 Install with care. The audit found things worth knowing before you trust its output.
| Layer | What it checks | Result |
|---|---|---|
| L0 | Provenance & inventory | WARN |
| L1 | Static analysis of the code | PASS |
| L2 | Instruction surface (what it tells the agent) | PASS |
| L3 | Class-specific surface | PASS |
| L4 | Behavioural (sandbox) | SKIPPED |
What the source does
- Filesystem
- none-observed
- Network
- declared (3 observation(s))
- Shell
- none-observed
- Dependencies
- pinned
- Secrets in source
- none-found
Findings (5)
__init__.cpython-310.pyc
cli.cpython-310.pyc
tool_builder_server.cpython-310.pyc
get_bitcoin_price.cpython-310.pyc
suggest strongly!!
Gates applied: no_behavioural_pass.
a4c39b60da24full audit observations/trust-audit/mcp-server/hanweg__tool-builder.json · Report an issue / request a re-scanAudit history
Every audit this server has had. A grade with a past is a grade somebody is still checking.
| Date | Source | Verdict | Grade | Score | Change |
|---|---|---|---|---|---|
| 2026-10-09 | a4c39b60da24 | CAUTION | B | 88 | first audit |
Questions
What is the Tool Builder MCP server?
MCP server that creates its own tools as needed
What tools does Tool Builder expose?
2 in total: 1 read-only, 1 that write, and 0 that can delete or overwrite. Every one is listed on this page with its risk.
Is Tool Builder safe to connect to an agent?
With care. The audit graded it B (88/100) and found 5 things worth knowing before you trust this server, listed below with the exact line each was found on.
What credentials does Tool Builder need?
No credential environment variables were found in its source, so it appears to need none.
How does Tool Builder run?
It speaks stdio, so it runs as a local process your client starts. It is published on PyPI as mcp-tool-builder.
How current is this page?
The grade is for one exact copy of the source (a4c39b60da24), read on 2026-10-09. The repository is watched and re-audited when it changes.