[jira] [Closed] (CAY-2936) Add a placeholder MCP server to the Modeler distribution

["Andrus Adamchik (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CAY-2936?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrus Adamchik closed CAY-2936.
--------------------------------
    Fix Version/s: 5.0-M2
       Resolution: Fixed

> Add a placeholder MCP server to the Modeler distribution
> --------------------------------------------------------
>
>                 Key: CAY-2936
>                 URL: https://issues.apache.org/jira/browse/CAY-2936
>             Project: Cayenne
>          Issue Type: Task
>            Reporter: Andrus Adamchik
>            Assignee: Andrus Adamchik
>            Priority: Major
>             Fix For: 5.0-M2
>
>
> h2. Summary
> Add a new {{cayenne-mcp-server}} Maven module that builds an executable jar implementing a minimal Model Context Protocol server. The jar ships inside every Modeler distribution. When a coding agent launches it, the server speaks MCP over stdio and exposes a single {{hello}} tool that returns {{"hello world"}}.
> h2. Background
> The Modeler distribution (cross-platform jar bundle, plus macOS and Windows app bundles) is the artifact users already install to work with Cayenne projects. To enable agent-driven workflows, we want an MCP server packaged inside that same distribution — no extra downloads, no separate install. This ticket lands the scaffolding and a placeholder tool, proving the end-to-end wiring from agent to MCP jar to a registered tool handler.
> h2. Goals
> * A new {{cayenne-mcp-server}} module that produces a single self-contained executable jar.
> * The jar is included in all three Modeler distribution archives at a known relative path.
> * The server speaks MCP over stdio and registers a {{hello}} tool that returns {{"hello world"}} when invoked.
> h2. Architecture
> {{cayenne-mcp-server}} depends on the official MCP Java SDK. Its {{main}} method configures stderr logging, builds an MCP server with the {{hello}} tool registered, and hands off to the SDK's stdio loop. The module is shaded into a single executable jar by {{maven-shade-plugin}}. The existing {{assembly}} module is updated to drop that jar into {{lib/mcp/}} of each Modeler distribution. Agents launch it with {{java -jar}}.
> h2. Launch contract
> The agent's MCP server config invokes:
> {code}
> java -jar <modeler-install>/lib/mcp/cayenne-mcp-server.jar
> {code}
> The placeholder takes no options other than {{-h}}/{{--help}} and {{-V}}/{{--version}}.
> h2. Logging
> Stdout is reserved for the MCP transport. All logs go to stderr. Capturing or surfacing stderr is the MCP host's responsibility. Logback is configured programmatically at boot with stdout appenders disabled.
> h2. Dependencies
> The MCP Java SDK ({{io.modelcontextprotocol.sdk:mcp}}), SLF4J + Logback, and Jackson (transitively via the SDK). Tests use JUnit 5 (already managed by the existing {{junit-bom}}).
> h2. Prerequisites
> Cayenne must be on Java 21 before this work starts — the MCP SDK requires Java 17+, and the JDK upgrade is being planned independently.
> h2. Acceptance criteria
> * {{mvn clean verify}} from the repo root builds the new module and includes its shaded jar in each of the three Modeler distribution archives at {{lib/mcp/cayenne-mcp-server.jar}}.
> * Launching the jar with {{java -jar}} starts an MCP server on stdio that successfully completes {{initialize}}, lists exactly one tool ({{hello}}) under {{tools/list}}, and returns {{"hello world"}} when that tool is called.
> * Nothing the server writes lands on stdout.
> * License/notice headers and Apache RAT pass on all new files.



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