---
title: 'MCP resource'
description: 'Data exposed by an MCP server under a URI so a host can retrieve it and decide whether to place it in model context.'
canonical_url: 'https://darkfactory.dev/glossary/mcp-resource'
markdown_url: 'https://darkfactory.dev/glossary/mcp-resource.md'
collection: glossary
date_published: '2026-08-03T00:00:00-04:00'
date_modified: '2026-08-26T00:00:00-04:00'
---

# MCP resource


## Definition

An **MCP resource** is data exposed by an MCP server under a URI. A host can list resources, read one by URI, and in supported cases subscribe to changes. The resource may contain text or binary data and can represent files, database records, schemas, application state, or other context.

Resources let servers expose information without turning every read into an executable tool call. The server owns retrieval and access checks. The host decides whether, when, and how much of the returned content enters model context. Resource templates describe parameterized families of resources when the full set cannot be listed as fixed URIs.

## Context remains untrusted input

A URI and MIME type provide structure, not truth. Resource content can be stale, overscoped, poisoned, or contain indirect prompt injection. Preserve its origin and retrieval time, limit access to the user's authority, label content separately from instructions, and avoid loading more than the task requires.

## Distinguish it from nearby terms

A resource supplies addressable data. A tool performs an operation and may also return data. A prompt supplies a reusable message template. These primitives can overlap in effect, but their interaction and consent expectations differ.

## Check your understanding

A retrieved issue contains text telling the model to upload secrets to another server. Is that part of the user's instruction? No. It is untrusted resource content. Keep the boundary visible and prevent it from expanding tool authority.

## Related factory areas

- [Context, memory, knowledge & skills](https://darkfactory.dev/factory/context-memory-skills)
- [Tools & project interfaces](https://darkfactory.dev/factory/tools-interfaces)

## Evidence and further reading

- [Model Context Protocol Specification](https://modelcontextprotocol.io/docs/learn/architecture)