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Resources

What are Resources?

Resources are data sources that AI models can read or subscribe to. Think of them as a way to provide context, data, or state to your AI interactions!

Understanding Resources​

Resources can be:

  • Files
  • API endpoints
  • Database queries
  • Real-time data streams
  • Configuration data

Here's a simple example:

import { MCPResource } from "mcp-framework";

class ConfigResource extends MCPResource {
  uri = "resource://config";
  name = "Configuration";
  description = "System configuration settings";
  mimeType = "application/json";

  async read() {
    return [
      {
        uri: this.uri,
        mimeType: this.mimeType,
        text: JSON.stringify({
          version: "1.0.0",
          environment: "production",
          features: ["analytics", "reporting"],
        }),
      },
    ];
  }
}

Creating Resources​

Using the CLI​

mcp add resource my-resource

This creates a new resource in src/resources/MyResource.ts.

Resource Structure​

Every resource has:

  1. Metadata
uri = "resource://my-data";
name = "My Data Resource";
description = "Provides access to my data";
mimeType = "application/json";
  1. Read Method
async read(): Promise<ResourceContent[]> {
  // Fetch or generate your data
  return [{
    uri: this.uri,
    mimeType: this.mimeType,
    text: JSON.stringify(data)
  }];
}

Resource Types​

Static Resources​

class DocumentationResource extends MCPResource {
  uri = "resource://docs";
  name = "Documentation";
  mimeType = "text/markdown";

  async read() {
    return [
      {
        uri: this.uri,
        mimeType: this.mimeType,
        text: "# API Documentation\n\nWelcome to our API...",
      },
    ];
  }
}

Dynamic Resources​

class MarketDataResource extends MCPResource {
  uri = "resource://market-data";
  name = "Market Data";
  mimeType = "application/json";

  async read() {
    const data = await this.fetch("https://api.market.com/latest");
    return [
      {
        uri: this.uri,
        mimeType: this.mimeType,
        text: JSON.stringify(data),
      },
    ];
  }
}

Real-time Resources​

Real-time Updates

Use subscription methods to handle real-time data streams!

class StockTickerResource extends MCPResource {
  uri = "resource://stock-ticker";
  name = "Stock Ticker";
  mimeType = "application/json";
  private ws: WebSocket | null = null;

  async subscribe() {
    this.ws = new WebSocket("wss://stocks.example.com");
    this.ws.on("message", this.handleUpdate);
  }

  async unsubscribe() {
    if (this.ws) {
      this.ws.close();
      this.ws = null;
    }
  }

  async read() {
    const latestData = await this.getLatestStockData();
    return [
      {
        uri: this.uri,
        mimeType: this.mimeType,
        text: JSON.stringify(latestData),
      },
    ];
  }
}

Best Practices​

  1. URI Naming
uri = "resource://domain/type/identifier";
// Example: "resource://finance/stocks/AAPL"
  1. Error Handling
async read() {
  try {
    const data = await this.fetchData();
    return [{
      uri: this.uri,
      mimeType: this.mimeType,
      text: JSON.stringify(data)
    }];
  } catch (error) {
    throw new Error(`Failed to read resource: ${error.message}`);
  }
}
  1. Caching
class CachedResource extends MCPResource {
  private cache: any = null;
  private lastFetch: number = 0;
  private TTL = 60000; // 1 minute

  async read() {
    if (this.cache && Date.now() - this.lastFetch < this.TTL) {
      return this.cache;
    }

    const data = await this.fetchFreshData();
    this.cache = data;
    this.lastFetch = Date.now();
    return data;
  }
}

Advanced Usage​

Combining with Tools​

class DataResource extends MCPResource {
  uri = "resource://data";
  name = "Data Store";

  async read() {
    return [
      {
        uri: this.uri,
        mimeType: "application/json",
        text: JSON.stringify(await this.getData()),
      },
    ];
  }
}

class DataProcessor extends MCPTool {
  async execute(input) {
    const resource = new DataResource();
    const [data] = await resource.read();
    return this.processData(JSON.parse(data.text));
  }
}

Next Steps​