Feat/mcp serve cli #2596

ntoledo319 · 2026-01-15T21:31:40Z

Summary

Implements #1926 - MCP Server for Golem CLI
This PR adds an MCP (Model Context Protocol) server mode to the Golem CLI, enabling AI agents and tools to interact with Golem programmatically.

Changes

Add --serve and --serve-port flags to enable MCP server mode
Expose all CLI leaf commands as MCP tools
Expose golem.yaml manifests as MCP resources
Use rmcp crate with HTTP Streamable transport
Add E2E tests for MCP functionality
Update README with MCP usage documentation

Usage

golem-cli --serve --serve-port 1232
MCP Methods Supported
initialize - Initialize MCP session
tools/list - List available CLI commands as tools
tools/call - Execute a CLI command
resources/list - List discovered golem.yaml manifests
resources/read - Read manifest contents
Testing
Manual testing performed with curl. E2E tests available:

bash
cargo test -p golem-cli mcp_e2e -- -

Implements issue golemcloud#1926 - MCP Server for Golem CLI - Add --serve and --serve-port flags to enable MCP server mode - Expose all CLI leaf commands as MCP tools - Expose golem.yaml manifests as MCP resources - Use rmcp crate with HTTP Streamable transport - Add E2E tests for MCP functionality - Update README with MCP usage documentation

Copilot

Pull request overview

This PR implements MCP (Model Context Protocol) server functionality for the Golem CLI, enabling AI agents to interact with Golem programmatically through HTTP-based JSON-RPC communication.

Changes:

Added new mcp module exposing CLI commands as MCP tools and golem.yaml manifests as MCP resources
Added comprehensive E2E tests for MCP server functionality
Updated dependencies to include rmcp and axum crates
Added MCP usage documentation to README

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
cli/golem-cli/src/mcp.rs	New MCP server implementation exposing CLI commands as tools and manifests as resources
cli/golem-cli/tests/mcp_e2e.rs	Comprehensive E2E tests for MCP server functionality
cli/golem-cli/src/lib.rs	Added mcp module to public exports
cli/golem-cli/Cargo.toml	Added rmcp and axum dependencies
README.md	Added MCP server mode documentation with usage examples

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Copilot · 2026-01-15T21:35:16Z

cli/golem-cli/src/mcp.rs

+/// Start the MCP server on the specified port
+///
+/// This function blocks until the server is shut down (Ctrl+C).
+///
+/// # Arguments
+/// * `port` - Port to listen on
+///
+/// # Example
+/// ```no_run
+/// # use golem_cli::mcp::run_mcp_server;
+/// # tokio::runtime::Runtime::new().unwrap().block_on(async {
+/// run_mcp_server(1232).await.unwrap();
+/// # });
+/// ```


The run_mcp_server function is publicly exported but there's no visible integration with the CLI's command-line argument parsing. The PR description mentions --serve and --serve-port flags, but these flags don't appear to be defined in the command structure (GolemCliCommand or GolemCliGlobalFlags). Without these flags being added to the CLI argument parser, this function cannot be invoked by users as documented. You need to either: (1) add the --serve and --serve-port flags to the command structure and wire them up in the command handler, or (2) update the documentation to clarify the actual invocation method.

Suggested change

/// Start the MCP server on the specified port

///

/// This function blocks until the server is shut down (Ctrl+C).

///

/// # Arguments

/// * `port` - Port to listen on

///

/// # Example

/// ```no_run

/// # use golem_cli::mcp::run_mcp_server;

/// # tokio::runtime::Runtime::new().unwrap().block_on(async {

/// run_mcp_server(1232).await.unwrap();

/// # });

/// ```

/// Start the MCP server on the specified port.

///

/// This is a **library entrypoint** used by callers that want to expose the

/// Golem CLI via the MCP protocol. Calling this function does **not** add any

/// command-line flags (such as `--serve` or `--serve-port`) on its own; it is

/// up to the embedding binary or CLI layer to define such flags and call

/// `run_mcp_server` with the appropriate port value.

///

/// This function blocks until the server is shut down (Ctrl+C or SIGTERM).

///

/// # Arguments

/// * `port` - Port to listen on

///

/// # Examples

///

/// Programmatic use from Rust:

///

/// ```no_run

/// # use golem_cli::mcp::run_mcp_server;

/// # tokio::runtime::Runtime::new().unwrap().block_on(async {

/// run_mcp_server(1232).await.unwrap();

/// # });

/// ```

///

/// A CLI wrapper (defined elsewhere) can parse flags such as `--serve` and

/// `--serve-port` and delegate to this function. This module does not define

/// or register those flags directly; it only provides the server runner.

Copilot · 2026-01-15T21:35:16Z

cli/golem-cli/tests/mcp_e2e.rs

+
+            let result = client
+                .call_tool(name, serde_json::json!({"args": ["--help"]}))
+                .expect(&format!("Failed to call tool: {}", name));


Using expect with a formatted string is inefficient because the string is allocated even when the Result is Ok. Replace with unwrap_or_else or use expect with a static string and include the error context in the panic message using the error's Display implementation.

Copilot · 2026-01-15T21:35:16Z

cli/golem-cli/tests/mcp_e2e.rs

+
+            let result = client
+                .read_resource(uri)
+                .expect(&format!("Failed to read resource: {}", uri));


Using expect with a formatted string is inefficient because the string is allocated even when the Result is Ok. Replace with unwrap_or_else or use expect with a static string and include the error context in the panic message using the error's Display implementation.

Suggested change

.expect(&format!("Failed to read resource: {}", uri));

.unwrap_or_else(|e| panic!("Failed to read resource {}: {}", uri, e));

Copilot · 2026-01-15T21:35:17Z

README.md

+# Call a tool (e.g., get help)
+curl -X POST http://127.0.0.1:1232/mcp \
+  -H "Content-Type: application/json" \
+  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"component","arguments":{"args":["--help"]}}}'


The example shows calling a tool named 'component', but based on the tool naming pattern in mcp.rs (line 162: format!(\"{}.{}\", prefix, path.join(\".\"))), the actual tool name would be something like 'golem-cli.component' (with the command_name prefix). This example may not work as shown and could confuse users. Either update the example to use the correct tool name format, or clarify in the documentation what the actual tool naming convention is.

Suggested change

# Call a tool (e.g., get help)

curl -X POST http://127.0.0.1:1232/mcp \

-H "Content-Type: application/json" \

-d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"component","arguments":{"args":["--help"]}}}'

# Call a tool (e.g., get help for the `component` command)

curl -X POST http://127.0.0.1:1232/mcp \

-H "Content-Type: application/json" \

-d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"golem-cli.component","arguments":{"args":["--help"]}}}'

Copilot · 2026-01-15T21:35:17Z

cli/golem-cli/src/mcp.rs

+
+/// Output from CLI tool execution
+///
+/// # HUMAN-VALIDATED 2025-01-15


The comment '# HUMAN-VALIDATED 2025-01-15' appears to be a marker for AI-assisted code review or validation. This type of internal process comment should not be included in production code. Remove this comment as it provides no value to future code maintainers and may confuse readers.

Suggested change

/// # HUMAN-VALIDATED 2025-01-15

Copilot · 2026-01-15T21:35:17Z

cli/golem-cli/src/mcp.rs

+    let server = GolemMcpServer::new()?;
+    let addr: SocketAddr = ([127, 0, 0, 1], port).into();
+
+    eprintln!("{} running MCP Server at port {}", command_name(), port);


Using eprintln! for informational server startup messages is unconventional. Informational messages typically go to stdout (println!), while stderr (eprintln!) is reserved for errors and warnings. Consider using println! instead, or better yet, use the info! logging macro which is already imported and used elsewhere in this module (line 481).

Suggested change

eprintln!("{} running MCP Server at port {}", command_name(), port);

info!("{} running MCP Server at port {}", command_name(), port);

ntoledo319 added 3 commits January 15, 2026 16:26

feat(cli): add ServeFlags and MCP handler integration

6757fb4

test: add MCP E2E tests

29c8263

Copilot AI review requested due to automatic review settings January 15, 2026 21:31

Copilot started reviewing on behalf of ntoledo319 January 15, 2026 21:32 View session

Copilot AI reviewed Jan 15, 2026

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Feat/mcp serve cli #2596

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	.expect(&format!("Failed to read resource: {}", uri));
	.unwrap_or_else(\|e\| panic!("Failed to read resource {}: {}", uri, e));

	eprintln!("{} running MCP Server at port {}", command_name(), port);
	info!("{} running MCP Server at port {}", command_name(), port);

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ntoledo319 commented Jan 15, 2026

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