Tools
fx uses tools to read and edit files, run commands, and gather information. Describe what you need in your prompt; fx chooses the tools and shows their results in the conversation.
Built-in tools
| Tools | Description |
|---|---|
glob_files, grep_files, read_file | Find files, search their contents, and read them |
write_file, edit_file | Create or update files |
shell | Run commands, including interactive programs and development servers |
web_search, web_fetch | Search the web and read public URLs |
vision | Analyze images for models without image input (AI Gateway) |
skill, install_skill | Read skill instructions and references, or install skills |
subagent | Delegate work to another agent |
capability_search | Find installed skills and configured MCP tools |
mcp_select_tool | Load a specific MCP tool for use |
mcp_features | Read MCP resources and use server prompts |
ask_user_question | Ask you for input |
read_tool_result | Search or read a stored tool result |
Models with image input analyze attached images directly. See Vision.
glob_files matches file paths with glob patterns. grep_files searches for literal text. MCP tools found by capability_search load automatically within the schema budget; mcp_select_tool selects one by name.
Background commands
fx can keep a development server or file watcher running while it continues working. Ask it to check the output, send input to an interactive program, or stop a command:
Start the development server and keep it running while you update the homepage.
The shell tool uses run to start a command, interact to read output or send input, and stop to end it. A running command remains available across prompts in the same conversation.
Large tool results
In saved conversations, fx stores large tool results separately and gives the model a preview and a handle. The agent uses read_tool_result to search that output or read a specific range, including after you resume the conversation.
max_tool_result_bytes sets the tool output budget for model context. Results stored for later reads can exceed this budget.
Scope and permissions
File and command tools start from the primary workspace. Additional directories extend that scope. Tool actions follow your permission mode and rules.