Rust MCP Preflight

Rust MCP Preflight

Check an MCP Registry listing before you publish it.

mcp-publisher validate checks the shape of server.json. It doesn't check that the registry will accept your package: that only happens at mcp-publisher publish, after the crate version is already on crates.io and can't be changed. Rust MCP Preflight runs those checks first.

• The README line. Fetches the README crates.io serves for the exact crate version and looks for mcp-name: <your server name>, matched the way the registry matches it (ported from the registry's own validator, internal/validators/registries/cargo.go; the registry's validators haven't changed since this port, checked 2026-11-06). Catches the line hidden in an HTML comment (crates.io strips comments), the line glued to the next word, and a near miss such as the wrong case.
• server.json. The rules mcp-publisher publish applies: $schema, the server name, and for every package exact versions (no latest, no ranges), the transport and no spaces in the identifier. For cargo packages also the crate version, no fileSha256 and registryBaseUrl. Plus warnings for runtimeHint, mismatched versions, and placeholders left over from mcp-publisher init.
• The server name. The rules publish applies, whether it's already listed, and which login its namespace needs (including GitHub organizations, which login github can't publish to yet, and the two ways that work: GitHub Actions OIDC or a token).

It only reads: crates.io, the official registry and the GitHub users API. It publishes nothing and needs no keys.

Install

Prebuilt, in seconds (needs cargo-binstall):

cargo binstall rust-mcp-preflight

From source (compiles, a few minutes the first time):

cargo install rust-mcp-preflight

Or download the binary for your platform from the release assets: Linux (x86_64, aarch64), macOS (Intel, Apple silicon) and Windows (x86_64), each with a .sha256 file. Prebuilt binaries start with 0.1.2; for an earlier version, cargo binstall falls back to QuickInstall or compiling from source.

Use it from a terminal or CI

rust-mcp-preflight server.json

It prints one line per check. It exits 0 when ready, 1 if anything fails, and 2 if the file can't be read:

Preflight: server.json  PASS  name "io.github.VoidNullable/lific" is a valid server name  PASS  packages[0]: cargo crate "lific"  WARN  VoidNullable is a GitHub organization. `mcp-publisher login github` can't publish to org namespaces yet (registry #1468). As an Owner of the organization, publish from GitHub Actions (`mcp-publisher login github-oidc`), or with a token: ...  INFO  already listed: latest 2.11.1 (active). Your next publish needs a new version number  PASS  README of lific 2.11.1 on crates.io contains `mcp-name: io.github.VoidNullable/lific`
Ready: no failures, 1 warning(s).

Use it from an MCP client

Run with no arguments, it serves MCP over stdio. Each client below starts it with the command rust-mcp-preflight, so the binary must be on your PATH (cargo binstall and cargo install put it in ~/.cargo/bin).

Claude Code

claude mcp add preflight -- rust-mcp-preflight

goose (extensions): for one session,

goose session --with-extension "rust-mcp-preflight"

or for every session, in ~/.config/goose/config.yaml:

extensions:  preflight:    name: preflight    cmd: rust-mcp-preflight    args: []    enabled: true    type: stdio    timeout: 300

VS Code (MCP configuration): adds it to your user profile,

code --add-mcp '{"name":"preflight","type":"stdio","command":"rust-mcp-preflight"}'

or for one workspace, in .vscode/mcp.json:

{ "servers": { "preflight": { "type": "stdio", "command": "rust-mcp-preflight" } } }

Cursor (MCP): in ~/.cursor/mcp.json, or .cursor/mcp.json in a project:

{ "mcpServers": { "preflight": { "type": "stdio", "command": "rust-mcp-preflight" } } }

Any other client that runs a local MCP server: the same command, rust-mcp-preflight, over stdio.

A result with a FAIL has isError set, like the CLI's exit 1: the check ran, and the listing isn't ready.

Where it fits

The order is: cargo publish (with the line in the README), then rust-mcp-preflight server.json, then mcp-publisher login github and mcp-publisher publish.

The full walk-through: Listing a Rust MCP server in the official MCP Registry.

The README check and the crates.io rules are for cargo packages. Other package types (npm, PyPI, mcpb and so on) get the shared rules, and their registry's own checks are listed as not run.

If crates.io or the README can't be reached, the README counts as not checked and the result is a failure, so a CI run never passes on a README it didn't see.

Links

• Repository: https://github.com/Wolfe-Jam/rust-mcp-preflight
• mcp-name: io.github.Wolfe-Jam/rust-mcp-preflight

License

MIT

More about me and my work: wolfejam.dev/info

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