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Documentation Index

Fetch the complete documentation index at: https://docs.sirenspec.dev/llms.txt

Use this file to discover all available pages before exploring further.

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What Is an Agent?

An agent is a named LLM configuration. It combines:
  • A model URI that specifies the provider and model to use.
  • A system prompt that shapes the model’s behaviour.
  • An optional guardrails list that overrides the workflow-level defaults.
Agents are declared once under the agents: key and reused by any number of nodes.

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Defining an Agent

agents:
  assistant:
    model: "openai:gpt-4o-mini"
    system: "You are a helpful assistant. Answer questions clearly and concisely."
FieldRequiredDescription
modelYesProvider URI — provider:model format (e.g. openai:gpt-4o-mini).
systemYesSystem prompt sent to the model on every call.
guardrailsNoList of guardrail names. Overrides workflow-level guardrails for this agent only.

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Model URI Format

The model field uses a provider:model URI: 
openai:gpt-4o-mini
anthropic:claude-haiku-4-5-20251001
ollama:llama3.2
See Providers for the full list of supported providers and their configuration.

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System Prompts

The system prompt is passed to the model as a system role message (OpenAI/Ollama) or as the top-level system parameter (Anthropic). Write prompts that are specific and task-focused: 
agents:
  classifier:
    model: "openai:gpt-4o-mini"
    system: |
      Classify the user's message into one of these intents: question, complaint, feedback, other.
      Respond with ONLY the intent label, nothing else.

  replier:
    model: "anthropic:claude-haiku-4-5-20251001"
    system: |
      You are a customer support agent. Compose a short, helpful reply
      appropriate for the user's intent.

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Per-Agent Guardrails

By default, every agent inherits the workflow-level guardrails: list (or ["injection"] if unset). You can override this per agent: 
guardrails:
  - injection
  - length

agents:
  summarizer:
    model: "openai:gpt-4o-mini"
    system: "Summarise the following text in one paragraph."
    guardrails: []   # disable all guardrails for this agent only

  responder:
    model: "openai:gpt-4o-mini"
    system: "You are a support agent."
    # inherits workflow-level guardrails: [injection, length]
An empty list ([]) disables all guardrails for that agent. See Guardrails for the available options.

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Multiple Agents in One Workflow

A workflow can define as many agents as needed. Each node binds to exactly one agent: 
agents:
  triage_agent:
    model: "openai:gpt-4o-mini"
    system: "Classify the request as 'refund' or 'general'. Reply with one word only."

  refund_handler:
    model: "openai:gpt-4o-mini"
    system: "You handle refund requests. Acknowledge warmly and explain the process."

  general_handler:
    model: "openai:gpt-4o-mini"
    system: "You are a helpful support agent. Answer the question clearly."

nodes:
  triage:
    agent: triage_agent
    writes: working.triage.intent

  handle_refund:
    agent: refund_handler
    writes: output.reply

  handle_general:
    agent: general_handler
    writes: output.reply

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How Agents Receive Input

Each node’s agent receives:
  1. System message — the agent’s system prompt.
  2. User message — the first (root) node gets the raw user input; subsequent nodes receive the output of the most recently completed node.
The agent response is written to the context path specified by the node’s writes field.