E0428: validators defined multiple times - Compilation fails with any protocol version feature

[JeyzDFoo]

The crate fails to compile when using any protocol version feature (2024_11_05, 2025_03_26, 2025_06_18, or draft) due to the validators module being defined multiple times.

Environment:

rust-mcp-schema: v0.7.5 (also affects git main branch)
rustc: 1.91.1
cargo: 1.91.1
OS: macOS
To Reproduce:

Create a new project:

Add to Cargo.toml:

Use in src/main.rs:

Run cargo build

Error Output:

Root Cause:

The define_schema_version! macro in src/generated_schema.rs is invoked for ALL protocol versions (2025_06_18, 2025_03_26, 2024_11_05, draft), and each invocation includes:

This causes multiple definitions of the validators module in the same scope, even when only one protocol version feature is enabled.

Affected Configurations:

✗ All protocol versions: 2024_11_05, 2025_03_26, 2025_06_18, draft
✗ With and without schema_utils feature
✗ Published v0.7.5 from crates.io
✗ Git main branch
Expected Behavior:

The crate should compile successfully when a single protocol version feature is enabled, with only that version's validators module included.

Suggested Fix:

The validators module should be conditionally included based on the active feature, or the macro should be restructured to avoid multiple definitions in the same scope.

[hashemix]

Hey @JeyzDFoo . I tried to re-produce the issue as you described.

I created a sample app, using Rust 1.91.1, installed rust-mcp-schema v0.7.5 and used it in main.rs. and it worked as expected. I attached a screen shot below that you can compare to yours.

Is it possible that you are activating multiple versions of the the schema?
just keep in mind that 2025_06_18 is enabled by default, if you wanna enable another version you need to set default-features = false in your cargo.toml as I pointed in the screen shot below.

If you still facing the error, please create a sample project on github and share it here so I can take a look, thanks.