agz-rust-coder

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agz-rust-coder is a standalone stdio MCP server for compiler-grounded Rust work. It runs bounded Cargo validation, audits source, resolves exact-version crate documentation, provides Rust Analyzer navigation, and returns write-free rename/refactor packages.

Identity

MCP package ownership marker: mcp-name: io.github.ugur-murat-alt/agz-rust-coder.

Install

cargo install agz-rust-coder --locked
agz-rust-coder --version

The package is source-distributed through crates.io. Release pages also provide prebuilt archives and SHA-256 checksums.

OpenCode

Add the installed binary to opencode.jsonc:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "servers": {
      "rust": {
        "type": "local",
        "command": ["agz-rust-coder"],
        "cwd": ".",
        "codemode": false,
        "timeout": {
          "startup": 30000,
          "catalog": 30000,
          "execution": 720000
        }
      }
    }
  }
}

The canonical current directory is the default authorized root. Add explicit roots with repeated --allow-root arguments when the client starts elsewhere. Client-provided MCP roots may narrow configured access but never widen it.

Tools

OpenCode commonly exposes grouped MCP tools as rust_*.

Every tool returns deterministic structured data plus an equivalent bounded text fallback. External data stays under untrustedData. Expected domain outcomes such as compiler failure, missing crates, or unavailable docs are typed results; invalid input, authorization failure, resource exhaustion, and unavailable semantic infrastructure are protocol errors.

Configuration

Precedence is CLI, then AGZ_RUST_CODER_* environment variables, then the explicit --config TOML file, then defaults. Environment keys use __ between sections, for example AGZ_RUST_CODER_GATE__HARD_TIMEOUT_MS=600000.

Run agz-rust-coder --help for every CLI field. The complete behavior and default table is in docs/tools.md.

Security

The server does not modify workspace source, but it is not an operating-system sandbox. Cargo build scripts, tests, procedural macros, local rustdoc, and opted-in Rust Analyzer workspace code execute with the server user's authority. Use a container or OS sandbox when that boundary is required.

• Workspace and dependency paths are canonicalized and fail closed.
• Cache, lease, journal, docs, and telemetry paths cannot overlap authorized roots.
• Child output, HTTP bodies, directory walks, edits, tasks, and telemetry are bounded.
• rename, refactor, and formatting checks return data only.
• Stdout is reserved for MCP framing; logs and panic output use stderr.

Report vulnerabilities privately as described in SECURITY.md.

Development

cargo fmt --all --check
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
cargo test --workspace --all-targets --all-features --locked --no-fail-fast
cargo +1.88.0 check --workspace --all-targets --all-features --locked
cargo build --release --locked
cargo run -p xtask -- protocol-smoke
cargo run -p xtask -- opencode-smoke
cargo run -p xtask -- benchmark-smoke

See CONTRIBUTING.md, architecture, tool reference, benchmark protocol, and CHANGELOG.md.

Canonical Links

• Repository: https://github.com/ugur-murat-alt/agz-rust-coder
• Crate: https://crates.io/crates/agz-rust-coder
• SDK docs: https://docs.rs/rmcp/3.1.4/rmcp/
• MCP 2025-11-25: https://modelcontextprotocol.io/specification/2025-11-25
• MCP 2026-07-28: https://modelcontextprotocol.io/specification/2026-07-28

License

MIT, Copyright (c) 2026 Ugur Murat Altintas.

Unreleased: see six-part correctness/efficiency work for streaming diagnostics, explicit validation options and opt-in acceleration.