Advanced Mode

Direct editing & variables

In Advanced Mode, the right-hand panel becomes a truly editable sheet: every field of the blueprint is an input, not read-only. Add the {{x}} variables feature and you can create prompts that get parameterized at runtime.

Direct editing

All blueprint fields become editable in Advanced Mode:

  • Name — simple text input
  • Description — 2-line textarea
  • Model — Claude Fable 5, Anthropic's most capable model
  • Tone — free-form input (e.g. "professional", "friendly")
  • System Prompt — resizable 8-line textarea, in monospace

The chat on the left can still fill in these fields. You can start a conversation, let the Builder draft a prompt, then manually refine the punctuation, the tone, or a specific detail without going back through the chat.

Direct editing = speedFor a one-word change, editing the textarea takes 3 seconds. Re-prompting the Builder takes 30. Advanced Mode is designed for fast iterations.

Variables {{x}} in the system prompt

You can drop placeholders into any field (mainly the system prompt) with the syntax {{variable_name}}. Names accept only letters, digits, and underscores.

text
You are a support assistant for {{company}}.
Always reply in {{language}} with a {{tone}} tone.
If you don't know, redirect to support@{{domain}}.

In this example, the system prompt contains 4 variables: company, language, tone, domain. The Variables section just below the system prompt lets you give each one a default value.

Automatic detection

As soon as you write a {{x}}variable that isn't defined in the Variables section, an orange warning appears below the textarea with an Add button that automatically creates the missing rows.

Substitution at deployment

Placeholders are replaced with their default values:

  • When you click Copy JSON or Copy cURL
  • When you click Deploy my agent (the agent stored and sent to Anthropic contains the resolved prompt)

A variable with no default value stays as {{x}} in the output — on purpose, so that you notice the omission rather than send an incomplete prompt to the agent.

Known V1 limitations

  • Variables are stored in sessionStorage, not in a database. They travel with the current draft but not across devices.
  • Substitution happens at deployment (one-shot). There is no system yet where the deployed agent can receive different values for each task.
  • The other fields (description, tone) are not substituted — we only process system for now.