Module core 

Core abstractions and types for the MCP SDK

This module contains the fundamental building blocks for MCP implementations, including error handling, resource management, tool execution, and prompt handling.

Core Concepts

Tools

Tools represent executable functions that can be called by the MCP protocol:

use prism_mcp_rs::core::{Tool, ToolBuilder, ToolHandler};
use prism_mcp_rs::core::error::{McpError, McpResult};
use std::collections::HashMap;
use prism_mcp_rs::protocol::types::{ToolInfo, ToolResult, ContentBlock};
use serde_json::{json, Value};
use async_trait::async_trait;

struct CalculatorTool;

#[async_trait]
impl ToolHandler for CalculatorTool {
    async fn call(&self, arguments: HashMap<String, Value>) -> McpResult<ToolResult> {
        // Tool implementation  
        Ok(ToolResult {
            content: vec![ContentBlock::Text {
                text: "Result: 42".to_string(),
                annotations: None,
                meta: None,
            }],
            is_error: Some(false),
            meta: None,
            structured_content: None,
        })
    }
}

// Build the tool with the handler
let tool = ToolBuilder::new("calculator")
    .description("Performs calculations")
    .build(CalculatorTool)?;

Resources

Resources provide access to external data sources:

use prism_mcp_rs::core::{Resource, ResourceHandler};
use prism_mcp_rs::core::error::McpResult;
use std::collections::HashMap;
use prism_mcp_rs::protocol::types::{ResourceContents, ContentBlock};
use prism_mcp_rs::core::{ResourceInfo};
use async_trait::async_trait;

struct FileResource;

#[async_trait]
impl ResourceHandler for FileResource {
    async fn read(
        &self,
        uri: &str,
        params: &HashMap<String, String>,
    ) -> McpResult<Vec<ResourceContents>> {
        Ok(vec![ResourceContents::Text {
            uri: uri.to_string(),
            mime_type: Some("text/plain".to_string()),
            text: "File contents".to_string(),
            meta: None,
        }])
    }
     
    async fn list(&self) -> McpResult<Vec<ResourceInfo>> {
        Ok(vec![])
    }
}

Prompts

Prompts provide reusable interaction templates:

use prism_mcp_rs::core::{Prompt, PromptHandler};
use prism_mcp_rs::core::error::McpResult;
use std::collections::HashMap;
use prism_mcp_rs::protocol::types::{PromptResult, PromptMessage, Role, ContentBlock};
use serde_json::Value;
use async_trait::async_trait;

struct GreetingPrompt;

#[async_trait]
impl PromptHandler for GreetingPrompt {
    async fn get(&self, arguments: HashMap<String, Value>) -> McpResult<PromptResult> {
        Ok(PromptResult {
            description: Some("A friendly greeting".to_string()),
            messages: vec![
                PromptMessage {
                    role: Role::Assistant,
                    content: ContentBlock::Text {
                        text: "Hello! How can I help you today?".to_string(),
                        annotations: None,
                        meta: None,
                    },
                }
            ],
            meta: None,
        })
    }
}

Error Handling

The SDK provides comprehensive error handling:

use prism_mcp_rs::core::{McpError, McpResult};

fn process_data() -> McpResult<String> {
    // Return errors using the ? operator
    let data = std::fs::read_to_string("data.txt")
        .map_err(|e| McpError::Io(e.to_string()))?;
     
    Ok(data)
}

Features

• Type-Safe Handlers: Strongly typed handler traits
• Async Support: All handlers are async by default
• Builder Patterns: Ergonomic construction APIs
• Validation: Built-in parameter validation
• Discovery: Tool discovery and metadata support

Re-exports

pub use completion::CompletionContext;

pub use completion::CompletionHandler;

pub use completion::CompositeCompletionHandler;

pub use completion::PromptCompletionHandler;

pub use completion::ResourceUriCompletionHandler;

pub use completion::ToolCompletionHandler;

pub use completion_handlers::CompositeCompletionHandler as ExtendedCompositeCompletionHandler;

pub use completion_handlers::FileSystemCompletionHandler;

pub use completion_handlers::FuzzyCompletionHandler;

pub use completion_handlers::SchemaCompletionHandler;

pub use error::McpError;

pub use error::McpResult;

pub use prompt::Prompt;

pub use prompt::PromptHandler;

pub use resource::Resource;

pub use resource::ResourceHandler;

pub use resource::ResourceTemplate;

pub use tool::MultiRoundToolCall;

pub use tool::MultiRoundToolHandler;

pub use tool::Tool;

pub use tool::ToolBuilder;

pub use tool::ToolHandler;

pub use tool_discovery::DeprecationCleanupPolicy;

pub use tool_discovery::DiscoveryCriteria;

pub use tool_discovery::DiscoveryResult;

pub use tool_discovery::GlobalToolStats;

pub use tool_discovery::ToolRegistry;

pub use tool_metadata::CategoryFilter;

pub use tool_metadata::DeprecationSeverity;

pub use tool_metadata::ImprovedToolMetadata;

pub use tool_metadata::ToolBehaviorHints;

pub use tool_metadata::ToolCategory;

pub use tool_metadata::ToolDeprecation;

pub use validation::ParameterType;

pub use validation::ParameterValidator;

pub use validation::ValidationConfig;

pub use crate::protocol::types::PromptArgument;

pub use crate::protocol::types::PromptInfo;

pub use crate::protocol::types::PromptMessage;

pub use crate::protocol::types::PromptResult;

pub use crate::protocol::types::ResourceInfo;

pub use crate::protocol::types::ToolInfo;

Modules

completion

Completion handling for MCP servers

completion_handlers

Practical completion handlers for common MCP use cases

enhanced_errors

Enhanced error types for better ergonomics Replaces generic String messages with structured errors

error

Error types for the MCP Rust SDK

health

Health-check primitives for MCP SDK applications.

logging

Structured logging for the MCP SDK

metrics

Metrics collection for the MCP SDK

prompt

Prompt system for MCP servers

resource

Resource system for MCP servers

retry

Retry and circuit-breaker primitives for MCP operations.

tool

Tool system for MCP servers

tool_discovery

Tool Discovery and Management System

tool_metadata

improved Tool Metadata System

validation

Complete tool validation system for MCP SDK