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Zio Ella

MCP Server

Scala 3 MCP Server on ZIO HTTP

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Updated Apr 14, 2025

About

A lightweight framework for building Model Context Protocol servers using Scala 3 and ZIO, enabling rapid development of AI tool services with built‑in tooling like time and weather examples.

Capabilities

Resources
Access data sources
Tools
Execute functions
Prompts
Pre-built templates
Sampling
AI model interactions

Overview of Zio Ella

Zio Ella is a lightweight, Scala 3‑centric framework that lets developers expose Model Context Protocol (MCP) servers using the powerful ZIO ecosystem and . By combining ZIO’s effect‑safe runtime with MCP’s declarative tool definitions, the framework solves a common pain point: building robust, type‑safe AI assistant backends that can be deployed quickly and evolve safely. For teams already invested in ZIO, Zio Ella removes the boilerplate of wiring HTTP endpoints, handling JSON serialization, and managing concurrency—leaving developers to focus on the business logic of their tools.

The core value proposition lies in its seamless integration with modern AI platforms. Once a service declares its capabilities, Zio Ella automatically generates the MCP endpoints required for tool invocation, prompt handling, and resource provisioning. Developers can write tools as ordinary ZIO effects, leveraging the full expressive power of Scala 3’s type system. For example, a time‑query tool or a weather lookup can be defined with minimal code, and the framework takes care of translating the MCP request into a ZIO effect, executing it safely, and returning the result in the expected format.

Key features of Zio Ella include:

  • Declarative capability definition – tools, arguments, and resources are specified in a concise DSL.
  • Effect‑safe execution – every tool runs inside ZIO, guaranteeing proper resource handling, cancellation, and error reporting.
  • Automatic server scaffolding – a single call spins up an HTTP server that conforms to the MCP spec.
  • ZIO stack compatibility – the framework integrates naturally with , logging, and other ZIO layers, enabling fine‑grained control over environment configuration.
  • Extensibility – being open source and in early development, the framework welcomes community contributions to add new MCP features or optimize performance.

Typical use cases span from internal tooling to public APIs. A data science team can expose a predictive model as an MCP tool, allowing Claude or other assistants to query the model without exposing raw endpoints. A DevOps pipeline might provide a “deploy‑to‑staging” tool, letting an AI assistant orchestrate deployments based on natural language commands. Because the server is built on ZIO, it scales effortlessly to handle concurrent requests and can be deployed in cloud environments or embedded within larger microservice architectures.

In summary, Zio Ella empowers developers to rapidly prototype and ship MCP‑compliant services while maintaining the safety, composability, and performance guarantees that ZIO is known for. Its declarative API, tight integration with the ZIO ecosystem, and focus on effect‑safe execution make it a standout choice for anyone looking to bridge AI assistants with real‑world data and functionality.