# `Codex.FunctionTool`
[🔗](https://github.com/nshkrdotcom/codex_sdk/blob/v0.16.1/lib/codex/function_tool.ex#L1)

Convenience macro for defining function-backed tools with JSON schemas.

Usage:

    defmodule MyTool do
      use Codex.FunctionTool,
        name: "add",
        description: "Adds numbers",
        parameters: %{left: :number, right: :number},
        handler: fn %{"left" => left, "right" => right}, _ctx ->
          {:ok, %{"sum" => left + right}}
        end
    end

Options:
  * `:name` - tool name (defaults to module name)
  * `:description` - human-friendly description
  * `:parameters` - map of parameter names to type atoms or schema maps
  * `:required` - list of required parameter names (defaults to all)
  * `:schema` - explicit JSON schema (overrides generated schema)
  * `:strict?` - when true sets `"additionalProperties": false` (default)
  * `:handler` - function to invoke (falls back to `handle/2` or `handle/1`)
  * `:enabled?` - predicate to gate invocation (arity 1 or 2)
  * `:on_error` - fallback handler invoked with the error (arity 2 or 3)

# `opts`

```elixir
@type opts() :: map() | keyword()
```

# `build_metadata`

```elixir
@spec build_metadata(opts()) :: map()
```

Constructs metadata map used for tool registration.

# `build_schema`

```elixir
@spec build_schema(map(), keyword() | map()) :: map()
```

Builds a JSON schema map from a parameter definition.

# `execute`

```elixir
@spec execute(module(), map(), map() | list() | String.t() | nil, map()) ::
  {:ok, term()} | {:error, term()}
```

Executes the configured handler with normalized arguments.

---

*Consult [api-reference.md](api-reference.md) for complete listing*