Call a Golem tool from MoonBit

Call an existing tool through a generated client

Load golem-generating-tool-clients for built-in releases and MCP imports. Add the tool to the MoonBit component’s dependencies.tools and configure its runtime binding separately. golem build automatically generates the client without an explicit bridge selection. Add the generated module as a local dependency, then import "bash-tool-guest-client/client" @bash in the consumer’s moon.pkg. Call the built-in bash release 0.2.1 inside an async agent method:

let client = @bash.BashClient::new()
defer client.drop()
match client.run("printf 'hello\\n'", "", 600U) {
  Ok(result) => result.stdout
  Err(_) => "bash failed"
}

Handle the actual tool error as appropriate for the agent, and check the script’s exit code in the successful result. Bash returns stdout and stderr as strings. For output attachments, the generated method starts a TypedToolInvocation synchronously; use its collect() helper from async code to drain outputs and check result, stdout, and stderr outcomes independently.

Call from a definition owned by the application

#derive.tool generates <Tool>Client in golem_tool_clients.mbt:

async fn call_echo() -> Result[String, @tool.ToolError[@tool.NoToolError]] {
  let client = EchoClient::new()
  defer client.drop()
  client.echo("hello")
}

Call generated tool methods from an async fn; MoonBit has no await keyword. Use new_for(name) when targeting another registration name. Generated signatures preserve custom errors and stream capabilities; handle the returned @tool.ToolError[E] rather than assuming every failure is a domain error. Always call drop() when finished, and never edit the generated client.