fujidaiti/dart-fix-hints

dart_fix_hints (WIP)

Overview

dart_fix_hints is a minimal Dart MCP server that exposes a tool to describe diagnostics by id(s). It communicates over stdio and is intended to be hosted by an AI agent or any MCP-compliant client.

Current tool

• name: describe_diagnostic
• input: Either { "id": string } or { "ids": string[] }
• output:
  • Single id: one TextContent with the description (error if unknown)
  • Multiple ids: an array of TextContent entries, each "id: description" (unknown as "id: <unknown>")

Install

dart pub get

Run

Start the server over stdio:

dart run bin/dart_fix_hints.dart

CLI flags:

• --help prints usage
• --version prints the server version

Using the tool

From an MCP client, call describe_diagnostic with arguments like:

{"id":"discarded_result"}

Or multiple ids:

{"ids":["discarded_result","unused_import"]}

The server returns TextContent entries as described above.

Project structure

• bin/dart_fix_hints.dart: CLI entrypoint and MCP server wiring. Defines MCPDiagnosticsServer, registers tools, and binds stdio.
• lib/diagnostics.dart: Diagnostic registry defined as const Map<String,String> kDiagnosticDescriptions with a lookupDescription(String) helper.
• pubspec.yaml: Declares a local path dependency on the MCP library.
• ai/pkgs/dart_mcp/: Local MCP library providing protocol types and stdio channel utilities (examples included in example/).
• tool/debug_client.dart: Interactive client for manual debugging; spawns the server, pretty-prints raw responses, and accepts space-separated ids.

Design notes

• Separation of concerns: Tool behavior (server) is isolated from data (diagnostics registry).
• Transport: Uses stdioChannel to ensure line-delimited JSON over stdio. The server avoids printing to stdout except for explicit CLI output (help/version).
• MCP integration: Implements an MCP server via ToolsSupport, registers tools with schemas, and returns CallToolResult content entries.
• Data source: Diagnostics are embedded in-code as a const map for compatibility with compiled executables.
• Extensibility: Add/modify diagnostics in lib/diagnostics.dart; add new tools by defining a Tool and registering it in MCPDiagnosticsServer.

Extend

1. Add a diagnostic: update kDiagnosticDescriptions in lib/diagnostics.dart.
2. Add a tool: define a new Tool, implement a handler, and register it in the server constructor.

See also

• How do I break a string in YAML over multiple lines?: A great free content on the internet that explains the YAML's mystrerious syntax of writing multiline strings.