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The embedded() method simplifies including resources in tool responses, reducing code duplication and making it easier to reference resources from within tools.

​
Basic usage

Use server.embedded() to include a resource in a tool’s response: 
import { FastMCP } from "fastmcp";
import { z } from "zod";

const server = new FastMCP({
  name: "My Server",
  version: "1.0.0",
});

// Define a resource
server.addResource({
  uri: "system://status",
  name: "System Status",
  mimeType: "text/plain",
  async load() {
    return {
      text: "System operational",
    };
  },
});

// Use embedded resource in a tool
server.addTool({
  name: "get_system_status",
  description: "Get current system status",
  parameters: z.object({}),
  execute: async () => {
    return {
      content: [
        {
          type: "resource",
          resource: await server.embedded("system://status"),
        },
      ],
    };
  },
});

​
With resource templates

Embedded resources work seamlessly with resource templates: 
// Define a resource template
server.addResourceTemplate({
  uriTemplate: "docs://project/{section}",
  name: "Project Documentation",
  mimeType: "text/markdown",
  arguments: [
    {
      name: "section",
      description: "Documentation section to retrieve",
      required: true,
    },
  ],
  async load(args) {
    const docs = {
      "getting-started": "# Getting Started\n\nWelcome to our project!",
      "api-reference": "# API Reference\n\nAuthentication is required.",
      "deployment": "# Deployment\n\nDeploy with Docker.",
    };
    return {
      text: docs[args.section] || "Documentation not found",
    };
  },
});

// Use embedded resource template in a tool
server.addTool({
  name: "get_documentation",
  description: "Retrieve project documentation",
  parameters: z.object({
    section: z.enum(["getting-started", "api-reference", "deployment"]),
  }),
  execute: async (args) => {
    return {
      content: [
        {
          type: "resource",
          resource: await server.embedded(`docs://project/${args.section}`),
        },
      ],
    };
  },
});

​
Multiple embedded resources

Include multiple resources in a single response: 
server.addTool({
  name: "get_user_profile",
  description: "Get complete user profile with all related data",
  parameters: z.object({
    userId: z.string(),
  }),
  execute: async (args) => {
    return {
      content: [
        {
          type: "text",
          text: `User Profile for ID: ${args.userId}`,
        },
        {
          type: "resource",
          resource: await server.embedded(`user://profile/${args.userId}`),
        },
        {
          type: "resource",
          resource: await server.embedded(`user://settings/${args.userId}`),
        },
        {
          type: "resource",
          resource: await server.embedded(`user://activity/${args.userId}`),
        },
      ],
    };
  },
});

​
Dynamic resource URIs

Construct resource URIs dynamically based on tool parameters: 
server.addResourceTemplate({
  uriTemplate: "data://{category}/{id}",
  name: "Data Item",
  mimeType: "application/json",
  arguments: [
    { name: "category", required: true },
    { name: "id", required: true },
  ],
  async load({ category, id }) {
    const data = await fetchFromDatabase(category, id);
    return { text: JSON.stringify(data) };
  },
});

server.addTool({
  name: "get_related_items",
  description: "Get an item and its related items",
  parameters: z.object({
    category: z.string(),
    id: z.string(),
  }),
  execute: async (args) => {
    // Get main item
    const mainItem = await server.embedded(
      `data://${args.category}/${args.id}`
    );

    // Get related items
    const relatedIds = await getRelatedIds(args.category, args.id);
    const relatedItems = await Promise.all(
      relatedIds.map((id) =>
        server.embedded(`data://${args.category}/${id}`)
      )
    );

    return {
      content: [
        { type: "text", text: "Main Item:" },
        { type: "resource", resource: mainItem },
        { type: "text", text: "\nRelated Items:" },
        ...relatedItems.map((resource) => ({
          type: "resource",
          resource,
        })),
      ],
    };
  },
});

​
With text and images

Combine embedded resources with text and images: 
import { imageContent } from "fastmcp";

server.addTool({
  name: "get_report",
  description: "Get a comprehensive report with data and visualizations",
  parameters: z.object({
    reportId: z.string(),
  }),
  execute: async (args) => {
    return {
      content: [
        {
          type: "text",
          text: `# Report ${args.reportId}\n\n`,
        },
        {
          type: "resource",
          resource: await server.embedded(`reports://data/${args.reportId}`),
        },
        {
          type: "text",
          text: "\n## Visualization\n\n",
        },
        await imageContent({
          url: `https://example.com/charts/${args.reportId}.png`,
        }),
      ],
    };
  },
});

​
Error handling

Handle errors when resources don’t exist: 
import { UserError } from "fastmcp";

server.addTool({
  name: "get_document",
  description: "Get a document by ID",
  parameters: z.object({
    documentId: z.string(),
  }),
  execute: async (args) => {
    try {
      const resource = await server.embedded(
        `docs://documents/${args.documentId}`
      );
      return {
        content: [
          {
            type: "resource",
            resource,
          },
        ],
      };
    } catch (error) {
      throw new UserError(
        `Document not found: ${args.documentId}`
      );
    }
  },
});

​
Best practices

1

Define resources separately

Define resources as standalone entities, then reference them in tools. This promotes reusability.
// Good: Reusable resource
server.addResource({
  uri: "config://app",
  name: "App Configuration",
  mimeType: "application/json",
  async load() {
    return { text: JSON.stringify(config) };
  },
});

// Multiple tools can use it
server.addTool({
  name: "get_config",
  execute: async () => ({
    content: [{ type: "resource", resource: await server.embedded("config://app") }],
  }),
});
2

Use descriptive URIs

Choose clear, hierarchical URI schemes that make the resource purpose obvious.
// Good: Clear hierarchy
"user://profile/{userId}"
"docs://api/{endpoint}"
"data://reports/{year}/{month}"

// Bad: Unclear structure
"resource://{id}"
"data://{type}"
3

Cache expensive operations

If resource loading is expensive, implement caching in the load function.
const cache = new Map();

server.addResource({
  uri: "expensive://computation",
  name: "Expensive Computation",
  mimeType: "application/json",
  async load() {
    if (cache.has("result")) {
      return { text: cache.get("result") };
    }
    const result = await expensiveOperation();
    cache.set("result", result);
    return { text: result };
  },
});
4

Document resource structure

Provide clear descriptions for resource templates to help users understand what they contain.
server.addResourceTemplate({
  uriTemplate: "users://{userId}/settings",
  name: "User Settings",
  description: "User-specific configuration including preferences, notifications, and privacy settings",
  mimeType: "application/json",
  // ...
});

​
Next steps

Resources

Learn more about defining resources

Tools

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