Templates and conditions

agntz uses a small templating language — handlebars-shaped, intentionally tiny — for variable interpolation in instructions, tool params, step inputs, and the output map. Conditional execution (when, until) uses the same syntax with a comparison-operator extension.

Variable interpolation

{{name}} is replaced with the resolved value from state.

instruction: |
  You are a writing assistant. Write about {{topic}} in a {{tone}} tone.

  {{#if feedback}}
  The reviewer provided feedback. Incorporate it:
  {{feedback}}
  {{/if}}

  {{#if language != en}}
  Write your response in {{language}}.
  {{/if}}

Rules:

• {{varName}} — replaced with the resolved value. Null renders as empty.
• Dotted paths like {{researcher.summary}} walk into a sub-agent's output.
• Unresolved references (skipped steps, first loop iteration) resolve to null — they don't throw.

Conditional blocks

{{#if varName}}                  # truthy: non-null, non-empty, non-zero
  ...
{{/if}}

{{#if varName == value}}          # equality
  ...
{{/if}}

{{#if varName != value}}          # inequality
  ...
{{/if}}

Blocks can be nested but cannot be parameterized — there's no {{#each}}, no helpers, no expression evaluation beyond == / !=.

Conditions in when and until

Used at step level (when) and at sequential level (until). Evaluated against the resolved state.

when: "{{language}} != en"
when: "{{feedback}}"                                     # truthiness
until: "{{score}} >= 0.8"
until: "{{score}} >= 0.8 && {{reviewer.approved}} == true"

Operators:

Truthiness = non-null, non-empty, non-zero. Strings, arrays, and objects are truthy if non-empty.

Special namespaces

Some {{...}} references aren't state lookups — they're resolved by the runtime against the environment or the workspace's secret store.

headers:
  Authorization: "Bearer {{env.SEARCH_KEY}}"   # embedded mode — reads process.env
  X-API-Key:     "{{secrets.WEATHER_TOKEN}}"   # hosted mode — reads workspace secrets

In hosted mode, {{env.X}} is intentionally restricted — multi-tenant workers don't share an environment with your code. Use {{secrets.X}} for credentials and configure them in Settings → Secrets on the hosted edition.

What's not in templates

agntz's templating is deliberately small. There's no:

• arbitrary expression evaluation
• loops ({{#each}})
• helpers / partials
• string transforms
• Math

If you need to compute something, do it in a tool agent and pin the result into state, or do it client-side before calling the agent.