rust-analyzer MCP Server
This is a Model Context Protocol (MCP) server that provides integration with rust-analyzer, allowing AI assistants to analyze Rust code, get hover information, find definitions, references, and more. Written in Rust for optimal performance and native integration.
Prerequisites
-
rust-analyzer: Make sure rust-analyzer is installed and available in your PATH
# Install via rustup (recommended) rustup component add rust-analyzer # Or install directly cargo install rust-analyzer # Verify installation rust-analyzer --version -
Rust: Version 1.70 or higher with Cargo
-
A Rust project: The server works best with a valid Rust workspace (containing
Cargo.toml)
Why Rust?
This Rust implementation offers several advantages over alternative implementations:
- Performance: Native Rust binary with minimal overhead
- Memory Safety: No runtime errors from memory issues
- Ecosystem Integration: Perfect fit for Rust development workflows
- Small Binary Size: Optimized release builds with LTO
- Concurrent Safety: Tokio async runtime handles multiple requests efficiently
- Native LSP Handling: Direct integration with rust-analyzer's protocol
Installation
From crates.io (Recommended)
Install directly from crates.io:
cargo install rust-analyzer-mcp
The binary will be installed to your Cargo bin directory (usually ~/.cargo/bin/rust-analyzer-mcp).
From Source
-
Clone the repository:
git clone https://github.com/zeenix/rust-analyzer-mcp.git cd rust-analyzer-mcp -
Build the project:
cargo build --release -
The binary will be available at
target/release/rust-analyzer-mcp
Configuration
Claude Code Configuration
Add an MCP server configuration to one of these locations:
Option 1: Project-specific (.mcp.json in your Rust project root):
{
"mcpServers": {
"rust-analyzer": {
"command": "rust-analyzer-mcp"
}
}
}
Option 2: User-wide (~/.claude.json or ~/.claude/settings.json):
{
"mcpServers": {
"rust-analyzer": {
"command": "rust-analyzer-mcp"
}
}
}
Note: If you installed from crates.io, the command will be in your PATH. If you built from source, use the full path to the binary. You can also configure servers using Claude Code's CLI wizard too.
Claude Desktop Configuration
Add this to your Claude Desktop configuration (claude_desktop_config.json):
{
"mcpServers": {
"rust-analyzer": {
"command": "rust-analyzer-mcp"
}
}
}
Note: If installed from crates.io, the command will be in your PATH. For Claude Desktop, you
may want to specify a cwd parameter if you want to analyze a specific project by default.
Cargo features
By default rust-analyzer analyses and checks your crate with whatever features its manifest makes default, so code behind a feature gate looks unresolved and its errors go unreported. Pass the features to use on the command line:
rust-analyzer-mcp --all-features /path/to/project
rust-analyzer-mcp --features serde,tokio /path/to/project
rust-analyzer-mcp --no-default-features --features serde /path/to/project
In a workspace, a feature may need naming with the package it belongs to, exactly as cargo wants
it: --features my-crate/serde.
Which features to use is a choice worth making per project rather than everywhere: --all-features
enables even the features a crate never expects to see enabled together, which for some projects
means analysis that fails or takes far longer than it needs to. Options go in args alongside the
command:
{
"mcpServers": {
"rust-analyzer": {
"command": "rust-analyzer-mcp",
"args": ["--features", "serde,tokio"]
}
}
}
Anything else rust-analyzer can be configured with is available through --config, which takes any
rust-analyzer setting without the
rust-analyzer. prefix. The value is read as JSON, or taken for a string if it is not JSON:
rust-analyzer-mcp --config check.command=clippy --config 'check.extraArgs=["--tests"]' .
Other MCP Clients
For other MCP clients, run the server with:
./target/release/rust-analyzer-mcp
Or during development:
cargo run
The server communicates via stdio and follows the MCP protocol.
Available Tools
Every file_path argument below may be given relative to the workspace root, as an absolute path,
or as a file: URI.
Working Features ✅
rust_analyzer_symbols
Get all symbols (functions, structs, enums, etc.) in a file.
Parameters:
file_path: Path to the Rust file
rust_analyzer_definition
Find the definition of a symbol at a specific position.
Parameters:
file_path: Path to the Rust fileline: Line number (0-based)character: Character position (0-based)
rust_analyzer_references
Find all references to a symbol at a specific position.
Parameters:
file_path: Path to the Rust fileline: Line number (0-based)character: Character position (0-based)
rust_analyzer_hover
Get hover information (documentation, type info) for a symbol at a specific position.
Parameters:
file_path: Path to the Rust file (relative to workspace)line: Line number (0-based)character: Character position (0-based)
rust_analyzer_completion
Get code completion suggestions at a specific position.
Parameters:
file_path: Path to the Rust fileline: Line number (0-based)character: Character position (0-based)
rust_analyzer_format
Format a Rust file using rust-analyzer's formatter. Returns an array of text edits to apply.
Parameters:
file_path: Path to the Rust file
Returns an empty array if the file is already formatted, or an array of edits with ranges and new text to apply.
rust_analyzer_code_actions
Get available code actions (quick fixes, refactorings) for a range.
Parameters:
file_path: Path to the Rust fileline: Start line number (0-based)character: Start character position (0-based)end_line: End line number (0-based)end_character: End character position (0-based)
Note: Code actions availability depends on:
- rust-analyzer being fully indexed
- Having actual code issues or refactoring opportunities in the selected range
- May return empty array if no actions are applicable
rust_analyzer_diagnostics
Get diagnostics (errors, warnings, hints) for a specific file.
Parameters:
file_path: Path to the Rust file
Runs a fresh cargo check and waits for it to finish, so the result describes the file as it is on
disk rather than as it was when first looked at. If the check does not finish in time, the result
says so in a note field and asking again picks up the rest.
Returns diagnostics with severity levels (error, warning, hint, information), messages, and location ranges. Includes a summary count of diagnostics by severity.
rust_analyzer_workspace_diagnostics
Get all diagnostics across the entire workspace.
Parameters: None
Returns aggregated diagnostics for all files in the workspace with file paths, severity levels, messages, and a summary of total counts by severity.
rust_analyzer_rename
Rename the symbol at a position, everywhere it is used in the workspace.
Parameters:
file_path: Path to the Rust fileline: Line number (0-based)character: Character position (0-based)new_name: The new name
Changes no files. It returns the edits to apply, each with the byte range it covers and the text it
replaces, listed last-first within each file so they can be applied one after another without
adjusting for the ones already made. It fails rather than answering while rust-analyzer is still
loading the workspace, since a rename worked out before then could miss references. Renaming a module also renames its file, which is reported
under file_operations; the untouched LSP WorkspaceEdit is included as workspace_edit.
rust_analyzer_set_workspace
Change the workspace root directory.
Parameters:
workspace_path: Path to the new workspace root
Usage Examples
Here are some example prompts you can use with Claude when this MCP server is configured:
-
Code Analysis:
Can you analyze the main function in src/main.rs and tell me what it does? Use the rust analyzer tools to get hover information and symbols. -
Finding Definitions:
I'm looking at a function call on line 25 of src/lib.rs at character position 10. Can you find its definition using rust-analyzer? -
Code Completion:
I'm writing code at line 15, character 8 in src/main.rs. What completion suggestions are available? -
Refactoring Help:
What code actions are available for the code between line 10-15 in src/utils.rs? -
Error Checking:
Can you get the diagnostics for src/main.rs and tell me about any errors or warnings? -
Workspace Analysis:
Show me all the diagnostics across the entire workspace using rust-analyzer.
Project Structure
rust-analyzer-mcp-server/
├── src/
│ └── main.rs # Main MCP server implementation
├── Cargo.toml # Rust dependencies and metadata
└── README.md # This file
Development
To run in development mode:
cargo run
To build for release:
cargo build --release
To run tests:
cargo test
To check code without building:
cargo check
For verbose logging during development:
RUST_LOG=debug cargo run
To run with release optimizations in dev:
cargo run --release
Troubleshooting
rust-analyzer not found
- Ensure rust-analyzer is in your PATH:
which rust-analyzer - Try reinstalling:
rustup component add rust-analyzer
Connection errors
- Make sure you're running the server in a valid Rust workspace (with Cargo.toml)
- Check that the file paths are correct and relative to the workspace root
Permission issues
- Make sure the server has read access to your Rust files
- Check that rust-analyzer has permission to analyze your project
LSP communication issues
- The server handles LSP protocol automatically
- Check console output for any rust-analyzer errors (use
RUST_LOG=debugfor verbose logging) - Ensure your Rust project compiles successfully
Build issues
- Make sure you have Rust 1.70+ installed:
rustc --version - Try
cargo cleanand rebuild if you encounter dependency issues
Performance
- rust-analyzer may take time to initially index large projects
- Subsequent requests should be much faster
- Consider excluding large target/ directories if needed
Contributing
This is a foundation implementation that covers the most common rust-analyzer features. Contributions are welcome for:
- Additional LSP methods (workspace symbols, call hierarchy, etc.)
- Better error handling and diagnostics
- Configuration options (via CLI args or config files)
- Performance optimizations and async improvements
- Integration tests and benchmarks
- Better LSP message parsing and error recovery
- Support for additional rust-analyzer features
Development Guidelines
- Use
cargo fmtfor consistent formatting - Run
cargo clippyfor linting - Add tests for new functionality
- Update documentation for new tools
- Follow Rust async best practices with Tokio
License
This project is licensed under the MIT License - see the LICENSE file for details.
