feat(ext-mcp): add MCP (Model Context Protocol) server extension

Streamable HTTP transport (JSON-RPC 2.0 over POST), one-class-per-tool/resource/prompt API mirroring RequestHandler, boot-time-precompiled schema/list payloads for a zero-alloc hot path, and optional OAuth2 protection built on flash-ext-oidc (lazy-loaded, RFC 8707 audience binding, RFC 9728 Protected Resource Metadata). Registers the module in the root and flash-extensions POMs and adds the ext-mcp commit scope to AGENTS.md. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-08-11 00:22:40 +00:00
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+# flash-ext-mcp
+
+`flash-ext-mcp` turns a Flash5 app into an [MCP](https://modelcontextprotocol.io) (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
+
+```java
+FlashApp.create(8080)
+    .install(new McpExtension(McpConfig.builder("my-mcp-server")
+        .toolsPackage("com.example.tools")
+        .build()))
+    .start();
+```
+
+```java
+@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`](tools-resources-prompts.md) — defining tools, resources, prompts
+- [`transport.md`](transport.md) — Streamable HTTP scope, session/SSE limitations, Origin validation
+- [`security.md`](security.md) — `McpSecurity` policy, OAuth2 resolution, RFC 9728 / RFC 8707
+- [`jackson-interop.md`](jackson-interop.md) — why this extension does not depend on `flash-ext-jackson`