Flash5/flash-extensions/flash-ext-mcp/docs

flash-ext-mcp

flash-ext-mcp turns a Flash5 app into an MCP (Model Context Protocol) server: JSON-RPC 2.0 over the Streamable HTTP transport, tools/resources/prompts declared as plain classes and discovered at boot, optional OAuth2 protection built on flash-ext-oidc.

Quick Start

FlashApp.create(8080)
    .install(new McpExtension(McpConfig.builder("my-mcp-server")
        .toolsPackage("com.example.tools")
        .build()))
    .start();

@Tool(name = "get_weather", description = "Get current weather for a city",
      args = @ToolArg(name = "city", description = "City name", required = true))
public class GetWeatherTool extends McpTool {

    private WeatherService weatherService;

    @Override
    protected void onInit() {
        weatherService = require(WeatherService.class);
    }

    @Override
    public ToolResponse call(ToolArguments args) {
        return ToolResponse.success(new TextContent(weatherService.fetch(args.getString("city"))));
    }
}

Operating Model

• One class per tool/resource/prompt — mirrors RequestHandler: a no-arg constructor, onInit() to cache services from FlashContext, one hot-path method (call/read/render). No CDI, no field injection, no reflection on the hot path.
• Boot-time precompilation — tools/list/resources/list/prompts/list JSON payloads (including JSON Schema) are built once at boot and spliced verbatim into responses. See tools-resources-prompts.md.
• Transport: Streamable HTTP, POST-only, stateless in this revision — see transport.md for exactly what that means and why.
• Security: optional, policy-driven OAuth2 via flash-ext-oidc — see security.md.
• JSON: this extension owns its JSON handling independently of flash-ext-jackson — see jackson-interop.md for why, and how a future opt-in reuse could work.

Documents

• tools-resources-prompts.md — defining tools, resources, prompts
• transport.md — Streamable HTTP scope, session/SSE limitations, Origin validation
• security.md — McpSecurity policy, OAuth2 resolution, RFC 9728 / RFC 8707
• jackson-interop.md — why this extension does not depend on flash-ext-jackson