Andrus Adamchik created CAY-2936:
------------------------------------
Summary: 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
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.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
