> ## Documentation Index
> Fetch the complete documentation index at: https://veryfront.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Tool

> How tools expose one typed capability to agents, workflows, or MCP servers.

A tool owns one callable capability. It defines input, output, and execution.

Tools exist because agents and workflows need safe ways to act. The model can
choose a tool, but the tool owns the deterministic code that runs.

## Characteristics

* Typed input describes what the caller must provide.
* Execution performs one operation.
* Output returns a structured result the caller can use.
* Errors describe why the operation could not complete.

## Boundary

Tools can be local project files, remote integration tools, or MCP-exposed
capabilities. The caller chooses when to invoke them. The tool owns how the work
runs.

Keep tools focused. A tool should do one thing, validate its input, and return a
clear result. If the operation grows into multiple stages, approvals, or retries,
move the coordination into a workflow.

## Wrong fit

Do not use a tool as a hidden workflow, long-running run, or large integration
layer. Use a workflow for process, a run for durable execution, and an
integration for reusable external service access.

For implementation steps, see [Tools](/code/guides/tools).