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