polytropos-mcp-0.1.0.2: README.md

# polytropos-mcp

Model Context Protocol (MCP) JSON-RPC 2.0 server implementation for [polytropos](https://github.com/NadiaYvette/polytropos) open records and variants.

## Overview

`polytropos-mcp` implements the Anthropic Model Context Protocol specification for agentic tooling. It leverages open product rows for compile-time OpenAPI 3.0 tool schema generation and open variant sum rows for $O(1)$ jump table tool call dispatch.

## Features

- **`recordToTool`**: Derives compliant OpenAPI 3.0 input schemas directly from open product row types (`Proxy (r :: Row)`).
- **`toolCallToVariant` & `dispatchToolCall`**: Parses JSON tool call arguments into open variants and executes handlers via `eliminateUniform`.
- **`runStdioServer`**: Complete stdio server loop handling lifecycle handshakes (`initialize`, `tools/list`, `tools/call`).

## Quick Example

```haskell
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE OverloadedRecordDot #-}
{-# LANGUAGE TypeApplications #-}
{-# OPTIONS_GHC -fplugin=Polytropos.Plugin #-}

import Data.Proxy (Proxy (..))
import Data.Text (Text)
import Polytropos
import Polytropos.MCP

-- Define tool parameter rows
type SearchArgs = '["query" ':= Text, "limit" ':= Int]
type EchoArgs   = '["message" ':= Text]

-- Tool registry as an open variant
type MyTools = Variant
  '[ "search" ':= SearchArgs
   , "echo"   ':= EchoArgs
   ]

-- Export tool specifications with OpenAPI schemas
tools :: [McpTool]
tools =
  [ recordToTool @"search" "Search indexed documents" (Proxy @SearchArgs)
  , recordToTool @"echo"   "Echo back a message"      (Proxy @EchoArgs)
  ]

-- Dispatch calls in O(1) jump table
handleCall :: MyTools -> IO [McpContent]
handleCall = eliminateUniform REC
  { search = \args -> pure [TextContent ("Found hits for: " <> args.query)]
  , echo   = \args -> pure [TextContent ("Echo: " <> args.message)]
  }
```

## License

Dual-licensed under `EUPL-1.2 OR Apache-2.0`.