Lesson Content

Resources – data, not functions.

Resources expose data for reading. A resource is identified by a URI and returns content when requested. Unlike tools (which execute a function), resources provide data that Claude or the user can read.

Examples of data appropriate for resources:

• A file or document (e.g., file:///path/to/document.md)
• A database record (e.g., db://customers/12345)
• A configuration object (e.g., config://app/settings)

When to use a resource vs. a tool: if the primary operation is reading static or semi-static data – use a resource. If the operation executes a function, makes a decision, or modifies state – use a tool.

Resource implementation pattern.

@app.list_resources()
async def list_resources() -> list[types.Resource]:
return [
types.Resource(
uri="docs://api-reference",
name="API Reference",
description="The full API reference documentation",
mimeType="text/markdown"
)
]

@app.read_resource()
async def read_resource(uri: str) -> str:
if uri == "docs://api-reference":
return Path("api_reference.md").read_text()
raise ValueError(f"Unknown resource: {uri}")

Prompts – reusable instruction templates.

Prompts are pre-defined instruction templates that users or AI clients can invoke by name. They produce a configured message ready to send to Claude – with or without dynamic parameters.

Examples:

• A code review prompt template with customizable language parameter
• A summarization prompt with configurable length and format parameters
• A debugging prompt template parameterized for error type

Prompts are reusable, shareable instructions – they capture best-practice prompt patterns and make them invocable by name across applications.

When to use which primitive.

• Primitive: Tool; Primary Use: Execute functions, take actions, retrieve dynamic data; Returns: Result of execution
• Primitive: Resource; Primary Use: Expose static or semi-static data for reading; Returns: Document content
• Primitive: Prompt; Primary Use: Provide reusable instruction templates; Returns: Configured message