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Ploston

LLM plans. Ploston executes.


The Problem

Today's AI agents orchestrate their own tool calls. The LLM decides which tool to call, interprets the result, decides the next step, and repeats—burning tokens and hallucinating along the way.

This creates five systemic failures:

Failure What Happens
Unreliable LLMs hallucinate steps, misuse tools, forget context mid-chain
Expensive Every action requires another LLM round-trip. Multi-step tasks explode in cost.
Non-deterministic Same request produces different behavior. Impossible to test or guarantee.
Opaque No audit trail. Just a blob of reasoning you can't inspect or replay.
Ungovernable No policy enforcement. No compliance. No safety guarantees.

No enterprise will deploy this in production. No developer wants to debug it.


The Solution

Ploston moves orchestration out of the LLM and into a deterministic runtime.

flowchart LR
    subgraph TODAY["TODAY"]
        A["LLM = planner + executor<br/>(fragile, expensive)"]
    end
    subgraph WITHPLOSTON["WITH Ploston"]
        B["LLM = planner"]
        C["Ploston = executor<br/>(deterministic, fast)"]
    end

You define workflows in YAML. Ploston exposes them as MCP tools. When your agent needs to scrape a website, transform the data, and publish it—it makes one call to your workflow. Ploston handles the rest.

Same inputs. Same outputs. Every time.


How It Works

flowchart TB
    Agent["Agent (Claude, GPT, etc.)"]
    Agent -->|"MCP call: workflow:scrape-and-publish"| Ploston

    subgraph Ploston["Ploston"]
        direction TB
        S1["Step 1: fetch_url"]
        S2["Step 2: extract_data"]
        S3["Step 3: validate_schema"]
        S4["Step 4: publish_to_kafka"]
        S1 --> S2 --> S3 --> S4

        Features["✓ Deterministic execution<br/>✓ Full trace and audit log<br/>✓ Built-in retry and errors"]
    end

    Ploston --> Result["Result returned to agent"]

The ✓ marks indicate guarantees Ploston provides: deterministic execution (same inputs → same outputs), complete audit trails, and automatic retry/error handling.

The agent doesn't orchestrate. It delegates to infrastructure that executes reliably.

Learn how this works →


Quick Start

# Install the CLI
pip install ploston-cli

# Run a workflow
ploston run workflows/hello-world.yaml

# Start as MCP server (connect to Claude Desktop)
ploston serve

Get Started →


What You Get

OSS (Available Now)

  • Workflow Engine — YAML-defined, deterministic execution
  • MCP Native — Expose workflows as tools agents can call
  • Python Code Steps — Sandboxed execution with 7-layer security
  • CLI — Manage, test, and run workflows locally
  • Telemetry — Execution traces and structured logging

Enterprise (Coming Soon)

  • Governance — RBAC, ABAC, policy enforcement
  • Advanced Workflows — Parallel execution, human approval, compensation
  • Pattern Mining — Detect repeated tool chains, suggest workflows
  • Workflow Synthesis — LLM-generated workflows from observed patterns
  • Cost Accounting — Track token savings, report ROI

See Roadmap →


Why Ploston?

Ploston is not an API gateway. It's not a workflow engine. It's not an agent framework.

It's the execution layer that makes agent systems production-ready.

Learn why this matters →


Architecture

flowchart TB
    Agent["AI Agent / Client"]

    Agent -->|"MCP Protocol / REST API"| Ploston

    subgraph Ploston["Ploston"]
        direction TB
        subgraph Components[" "]
            direction LR
            WE["Workflow<br/>Engine"]
            TR["Tool<br/>Registry"]
            MF["MCP Frontend<br/>(stdio or HTTP)"]
        end
        Sandbox["Python Sandbox (Code Steps)"]
        Components --> Sandbox
    end

    Ploston -->|"MCP Protocol"| External

    subgraph External["External MCP Servers"]
        Tools["filesystem, fetch, databases, custom tools, etc."]
    end

Key Concepts

Concept Description
Workflow A YAML file defining a sequence of steps to execute
Step Either a code step (Python) or a tool step (MCP tool call)
MCP Server External service providing tools via Model Context Protocol
Tool A function that can be called from workflows or by AI agents

Documentation

Getting Started

Guide Description
Installation Install from source or Docker
Quickstart 5-minute introduction to Ploston
First Workflow Step-by-step workflow tutorial

Concepts

Concept Description
How Ploston Works Core mental model: planning vs execution
Execution Model Step execution, data flow, error handling
Security Model 7-layer sandbox security
Workflows as Tools Virtual tool publishing via MCP

Guides

Guide Description
Workflow Authoring Complete guide to writing workflows
Code Steps Using Python code in workflows
Tool Integration Connecting MCP tools
Troubleshooting Common issues and solutions

Reference

Reference Description
CLI Reference All CLI commands and options
Workflow Schema Complete YAML schema reference
Configuration Configuration file options
Error Codes Error codes and resolutions

Examples

Example Description
Web Scraping Extract data from websites
Data Processing Transform and process data
API Integration Integrate with external APIs

System Requirements

  • Python: 3.12 or higher
  • OS: macOS, Linux, Windows
  • Memory: 512MB minimum, 1GB recommended

Getting Help


License

Ploston is released under the Apache 2.0 License.