Bug

Template expressions in elicitation step message fields (e.g. {{.params.owner}}) are not expanded — the raw placeholders are passed through to the client.

Example

- id: approval
  type: elicitation
  message: >
    PR #{{.params.pullNumber}} context gathered. Create a pending
    review on {{.params.owner}}/{{.params.repo}}?

Displays the literal {{.params.pullNumber}} instead of the resolved value.

Root cause

In pkg/vmcp/composer/workflow_engine.go, tool step arguments are explicitly expanded via templateExpander.Expand() (~line 404), but executeElicitationStep() (~line 639) passes step.Elicitation directly to RequestElicitation() without any template expansion.

The elicitation handler in pkg/vmcp/composer/elicitation_handler.go (~line 168) then passes the raw config.Message straight into the MCP elicitation request.

Suggested fix

Expand step.Elicitation.Message through the template expander before passing it to RequestElicitation() in executeElicitationStep(). Something like:

expandedMessage, err := e.templateExpander.Expand(ctx, step.Elicitation.Message, workflowCtx)
if err != nil {
    return fmt.Errorf("failed to expand elicitation message: %w", err)
}
step.Elicitation.Message = expandedMessage.(string)

Related

Documentation gaps for composite tools tracked in stacklok/docs-website#627.