cratedocs-mcp/docs/development.md
2025-03-06 22:51:01 -08:00

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# Development Guide
This guide provides information for developers who want to contribute to or modify the CrateDocs MCP server.
## Architecture Overview
The server consists of several key components:
1. **DocRouter** (`src/docs.rs`):
- Core implementation of the MCP Router trait
- Handles tool calls for documentation lookup
- Implements caching to avoid redundant API requests
2. **Transport Implementations**:
- STDIN/STDOUT server (`src/bin/doc_server.rs`)
- HTTP/SSE server (`src/bin/axum_docs.rs`)
3. **Utilities**:
- JSON-RPC frame codec for byte stream handling
## Adding New Features
### Adding a New Tool
To add a new tool to the documentation server:
1. Add the implementation function in `DocRouter` struct
2. Add the tool definition to the `list_tools()` method
3. Add the tool handler in the `call_tool()` match statement
Example:
```rust
// 1. Add the implementation function
async fn get_crate_examples(&self, crate_name: String, limit: Option<u32>) -> Result<String, ToolError> {
// Implementation details...
}
// 2. In list_tools() add:
Tool::new(
"get_crate_examples".to_string(),
"Get usage examples for a Rust crate".to_string(),
json!({
"type": "object",
"properties": {
"crate_name": {
"type": "string",
"description": "The name of the crate"
},
"limit": {
"type": "integer",
"description": "Maximum number of examples to return"
}
},
"required": ["crate_name"]
}),
),
// 3. In call_tool() match statement:
"get_crate_examples" => {
let crate_name = arguments
.get("crate_name")
.and_then(|v| v.as_str())
.ok_or_else(|| ToolError::InvalidParameters("crate_name is required".to_string()))?
.to_string();
let limit = arguments
.get("limit")
.and_then(|v| v.as_u64())
.map(|v| v as u32);
let examples = this.get_crate_examples(crate_name, limit).await?;
Ok(vec![Content::text(examples)])
}
```
### Enhancing the Cache
The current cache implementation is basic. To enhance it:
1. Add TTL (Time-To-Live) for cache entries
2. Add cache size limits to prevent memory issues
3. Consider using a more sophisticated caching library
## Testing
Create test files that implement basic tests for the server:
```rust
#[cfg(test)]
mod tests {
use super::*;
use tokio::test;
#[test]
async fn test_search_crates() {
let router = DocRouter::new();
let result = router.search_crates("tokio".to_string(), Some(2)).await;
assert!(result.is_ok());
let data = result.unwrap();
assert!(data.contains("crates"));
}
#[test]
async fn test_lookup_crate() {
let router = DocRouter::new();
let result = router.lookup_crate("serde".to_string(), None).await;
assert!(result.is_ok());
let data = result.unwrap();
assert!(data.contains("serde"));
}
}
```
## Deployment
For production deployment, consider:
1. Rate limiting to prevent abuse
2. Authentication for sensitive documentation
3. HTTPS for secure communication
4. Docker containerization for easier deployment
Example Dockerfile:
```dockerfile
FROM rust:1.74-slim as builder
WORKDIR /usr/src/app
COPY . .
RUN cargo build --release
FROM debian:stable-slim
RUN apt-get update && apt-get install -y libssl-dev ca-certificates && rm -rf /var/lib/apt/lists/*
COPY --from=builder /usr/src/app/target/release/axum-docs /usr/local/bin/
EXPOSE 8080
CMD ["axum-docs"]
```