Edict MCP Server

Edict

A programming language designed for AI agents. No parser. No syntax. Agents produce AST directly as JSON.

Edict is a statically-typed, effect-tracked programming language where the canonical program format is a JSON AST. It's purpose-built so AI agents can write, verify, and execute programs through a structured pipeline — no text parsing, no human-readable syntax, no ambiguity.

Agent (LLM)
  │  produces JSON AST via MCP tool call
  ↓
Schema Validator ─── invalid? → StructuredError → Agent retries
  ↓
Name Resolver ────── undefined? → StructuredError + candidates → Agent retries
  ↓
Type Checker ─────── mismatch? → StructuredError + expected type → Agent retries
  ↓
Effect Checker ───── violation? → StructuredError + propagation chain → Agent retries
  ↓
Contract Verifier ── unproven? → StructuredError + counterexample → Agent retries
  (Z3/SMT)            ↓
                  Code Generator (pure-JS WASM encoder) → WASM → Execute

Features

• JSON AST — Programs are JSON objects, not text files. No lexer, no parser.
• Structured errors — Every error is a typed JSON object with enough context for an agent to self-repair.
• Type system — Int, Float, String, Bool, Array<T>, Option<T>, Result<T,E>, records, enums, refinement types.
• Effect tracking — Functions declare pure, reads, writes, io, fails. The compiler verifies consistency.
• Contract verification — Pre/post conditions verified at compile time by Z3 (via SMT). Failing contracts return concrete counterexamples.
• WASM compilation — Verified programs compile to WebAssembly via a pure-JS encoder and run in Node.js.
• MCP interface — All tools exposed via Model Context Protocol for direct agent integration.
• Schema migration — ASTs from older schema versions are auto-migrated. No breakage when the language evolves.

Execution Model

Edict compiles to WebAssembly and runs in a sandboxed VM. This is a deliberate security decision — not a limitation:

• No ambient authority — compiled WASM cannot access the filesystem, network, or OS unless the host explicitly provides those capabilities via the pluggable EdictHostAdapter interface
• Compile-time capability declaration — the effect system (io, reads, writes, fails) lets the host inspect what a program requires before running it
• Runtime enforcement — RunLimits controls execution timeout, memory ceiling, and filesystem sandboxing
• Defense-in-depth — agent-generated code that runs immediately needs stronger isolation than human-reviewed code. The effect system + WASM sandbox + host adapter pattern provides exactly that

Host capabilities available through adapters: filesystem (sandboxed), HTTP, crypto (SHA-256, MD5, HMAC), environment variables, CLI arguments. New capabilities are added by extending EdictHostAdapter.

Quick Start

For AI Agents (MCP)

The fastest way to use Edict is through the MCP server — it exposes the entire compiler pipeline as tool calls:

npx edict-lang          # start MCP server (stdio transport, no install needed)

Or install locally:

npm install edict-lang
npx edict-lang          # start MCP server

Two calls to get started: edict_schema (learn the AST format) → edict_check (submit a program). See MCP Tools for the full tool list.

For Development

npm install
npm test          # 2675 tests across 136 files
npm run mcp       # start MCP server (stdio transport)

Docker

Run the Edict MCP server in a container — no local Node.js required:

# stdio transport (default — for local MCP clients)
docker run -i ghcr.io/sowiedu/edict

# HTTP transport (for remote/networked MCP clients)
docker run -p 3000:3000 -e EDICT_TRANSPORT=http ghcr.io/sowiedu/edict

Supported platforms: linux/amd64, linux/arm64.

Browser

Run the Edict compiler entirely in the browser — no server required:

import { compileBrowser, runBrowserDirect } from 'edict-lang/browser-full';

const result = compileBrowser(astJson);
if