galet-tools

Self-contained generic tool handlers and the handler framework they run on.

Lineage

This package is extracted from the Lucy monorepo (src/handlers) as described in the Lucy design doc software/ai/lucy/design/handlers-extraction.md and the plan software/ai/lucy/plan/handlers-extraction.md.

It is a fresh repository with no shared git history. Handler logic moves verbatim; the only intentional changes are the import namespace (src.handlers.* -> galet_tools.*) and the configuration boundary: tools depend on narrow port interfaces owned by this package (ConfigProvider, StorageLocationResolver, SandboxRootResolver, SecurityPolicy, ...), never on Lucy's ConfigManager. Lucy implements those ports at its composition root.

Features

• Handler framework — HandlerV2 ABC, HandlerRegistry, schema handling, and permission filtering.
• Generic tools — file_load, file_save, patch_apply, execute_command, execute_command2, generate_svg, and generate_image, registered under their existing names. file_load supports bounded line-range reads.
• Ports — sibling-owned interfaces the host implements, keeping the tools free of any host dependency.
• Handler discovery — installed packages can contribute handlers through Python package entry points without changing Lucy or galet-tools.

Quick start

python -m venv .venv
.venv/bin/pip install -e .

Run the suite:

python -m pytest -q

Using the registry in a host

Galet owns the handler contract and base registry. A host such as Lucy composes the generic handlers, its own host-specific handlers, and installed extension packages:

from galet_tools import HandlerRegistry, register_installed_handlers
from galet_tools.register_generic_defaults import register_generic_defaults

registry = HandlerRegistry()
register_generic_defaults(registry)
register_lucy_handlers(registry)
register_installed_handlers(registry)

Discovery adds installed capabilities to the registry; it does not grant them to an agent. The host should continue to apply its agent and context allowlists when selecting tool definitions.

Creating a handler extension

An extension package declares a registrar in its pyproject.toml:

[project.entry-points."galet_tools.handlers"]
web = "galet_web_tools:register"

The target is a callable that receives the shared registry:

def register(registry):
    registry.register(SearchHandler)
    registry.register(FetchHandler)

Entry points are loaded in deterministic name order. A plugin that cannot be loaded, does not resolve to a callable, or fails during registration raises HandlerPluginError with the responsible entry-point name. This is intentionally fail-fast so a host cannot start with an unexpectedly incomplete tool set.

MCP server

An optional MCP (Model Context Protocol) server exposes the generic tools over streamable HTTP. Install the extra:

.venv/bin/pip install -e '.[mcp]'

Copy the example config and start the server:

cp galet-mcp.example.json galet-mcp.json
galet-tools-mcp

galet-tools-mcp reads galet-mcp.json from the current directory by default; point it elsewhere with --config <path>.

Configuration

galet-mcp.json mirrors galet-mcp.example.json. Required keys are account, storage_root, storage_namespace, and sandbox_root; a null, blank, or (for the two path keys) relative value fails validation. Optional keys left out or set to null fall back to their defaults:

• allowlist — tools to expose; the default includes file_load, file_save, patch_apply, legacy execute_command, structured execute_command2, generate_svg, and generate_image.
• external_roots — named external roots the tools may access; default none.
• host — default 127.0.0.1; loopback only.
• port — default 8765.
• fonts — font paths for the generators; default none.

What it exposes

tools/list and tools/call over streamable HTTP at http://127.0.0.1:8765/mcp.

Smoke-test from the CLI

galet-tools-smoke is the end-to-end CLI client: it connects over HTTP (streamable HTTP) to a running galet MCP server using the official MCP SDK and performs real tools/list and tools/call round trips.

galet-tools-smoke list
galet-tools-smoke list --json
galet-tools-smoke call <tool> '<json args>'

The default URL is http://127.0.0.1:8765/mcp; override it with --url. The default read timeout is 30s; override it with --timeout.

Example round trip (storage root from galet-mcp.json):

galet-tools-smoke call file_save '{"path":"smoke/hello.txt","file_content":"hello galet smoke"}'
galet-tools-smoke call file_load '{"path":"smoke/hello.txt"}'
galet-tools-smoke call execute_command2 '{"mode":"process","executable":"python","arguments":["-c","print(123)"],"script":"","shell":"none","location":"sandbox","external_root":"","working_directory":".","timeout_seconds":30,"success_exit_codes":[0]}'

Exit codes: 0 ok; 1 tool reported an error (isError); 2 usage or bad JSON; 3 could not reach the server.

Fail-closed behaviour

The server refuses to start when the allowlist is empty or has no overlap with the registered tools, and only the advertised tools are callable. Unknown tool names in the allowlist fail validation.

Security

Binding is loopback-only by design: host must resolve to a loopback address. Remote access needs a separate reverse-proxy design.

License

MIT — see LICENSE.