One YAML = Any Agent.

A Rust framework for building AI agents from a single YAML specification. No code required for common use cases.

ai-agents.rs - Documentation, guides, and examples

• Declarative behavior - everything in YAML, not code
• Language-agnostic semantics - intent, extraction, validation via LLM (no regex)
• Layered overrides - global → agent → state → skill → turn
• Safety by default - tool policies, HITL approvals, error recovery
• Extensible - custom LLMs, tools, memory, storage, hooks

Status: 1.0.0-rc.9 — Under active development. APIs and YAML schema may change between minor versions.

• Multi-LLM with fallback - 12 providers (OpenAI, Anthropic, Google, Ollama, DeepSeek, Groq, Mistral, Cohere, xAI, Phind, OpenRouter, any OpenAI-compatible); named aliases (default, router); auto-fallback on failure
• Hierarchical state machine - nested sub-states, LLM-evaluated transitions, guard-based short-circuiting, intent-based routing, entry/exit actions
• Skill system - reusable tool + prompt workflows with LLM-based intent routing
• built-in tools + MCP - datetime, JSON, HTTP, file, text, template, math, calculator, random, echo; connect any MCP server for hundreds more
• Tool scoping & conditions - 3-level filtering (state → spec → registry), context/state/time/semantic conditions, multi-language aliases, parallel execution
• Input/output process pipeline - normalize, detect, extract, sanitize, validate, transform, format - all LLM-based, works across languages
• CompactingMemory - LLM-based rolling summarization, token budgeting, SQLite/Redis/file persistence
• Dynamic context - runtime, file, HTTP, env, and callback sources with Jinja2 templates in prompts
• Reasoning & reflection - chain-of-thought, ReAct, plan-and-execute, auto mode; LLM self-evaluation with criteria and retry
• Intent disambiguation - LLM-based ambiguity detection, clarification generation, multi-turn resolution
• Safety & control - error recovery with backoff, tool security (rate limits, domain restrictions), human-in-the-loop approvals with multi-language messages
• Dynamic agent spawning - runtime agent creation from YAML/templates, agent registry, inter-agent messaging
• Extensible via traits - LLMProvider, Memory, Tool, ApprovalHandler, Summarizer, AgentHooks, ToolProvider

See Concepts for architecture details and Providers for per-provider setup.

[dependencies]
ai-agents = "1.0.0-rc.9"

Create agent.yaml:

# agent.yaml
name: MyAgent
system_prompt: "You are a helpful assistant."
llm:
  provider: openai
  model: gpt-4.1-nano

# For any OpenAI-compatible server:
# llm:
#   provider: openai-compatible
#   model: qwen3:8b
#   base_url: http://localhost:11434/v1

# Provider-specific extra params are also allowed.
# Example for OpenAI reasoning-capable models:
# llms:
#   default:
#     provider: openai
#     model: gpt-5.4-mini
#     reasoning_effort: low
# llm:
#   default: default

Run it:

cargo run -p ai-agents-cli -- run agent.yaml

use ai_agents::{Agent, AgentBuilder};

#[tokio::main]
async fn main() -> ai_agents::Result<()> {
    let agent = AgentBuilder::from_yaml_file("agent.yaml")?
        .auto_configure_llms()?
        .auto_configure_features()?
        .build()?;

    let response = agent.chat("Hello!").await?;
    println!("{}", response.content);
    Ok(())
}

use ai_agents::{AgentBuilder, UnifiedLLMProvider, ProviderType};
use std::sync::Arc;

#[tokio::main]
async fn main() -> ai_agents::Result<()> {
    let llm = UnifiedLLMProvider::from_env(ProviderType::OpenAI, "gpt-4.1-nano")?;

    let agent = AgentBuilder::new()
        .system_prompt("You are a helpful assistant.")
        .llm(Arc::new(llm))
        .build()?;

    let response = agent.chat("Hello!").await?;
    println!("{}", response.content);
    Ok(())
}

See the examples/ directory for more.

# Install from crates.io
cargo install ai-agents-cli --version 1.0.0-rc.9

# Or run directly from source
cargo run -p ai-agents-cli -- run agent.yaml

ai-agents-cli run agent.yaml                          # interactive REPL
ai-agents-cli run agent.yaml --stream --show-tools     # stream tokens, show tool calls
ai-agents-cli run agent.yaml --show-state --show-timing # show state transitions and timing
ai-agents-cli validate agent.yaml                      # check YAML without starting

See the CLI Guide for REPL commands, metadata configuration, and full reference.

See the full roadmap for what's shipped, what's next, and the complete feature catalog.

This repository is an independent open-source project maintained by the author in a personal capacity.

It is not an official product or offering of any employer, and no employer owns or governs this project.

See INDEPENDENCE.md for details.

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT)