Phase 8Module 5 of 25

Resources

Not everything should be a tool call. Dumping a schema through a tool wastes a round trip. Resources are the shelf of reference books.

Tools are verbs. Resources are nouns. You open a cookbook (resource). You cook the meal (tool).

Visual Workflows

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Overview

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Preload a schema

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A Postgres server can expose db://schema/public so the agent knows tables before it queries.

Key Takeaways

1.Resources are readable data — files, schemas, docs — not actions. Each resource has a URI, a name, and usually a mime type.
2.Clients call list_resources then read_resource when they need context. Use a resource for lookup; use a tool when something must change.
3.URI schemes can be file://, db://, or your own (jira://project/KEY). Keep resources small enough to fit in context.
4.Huge dumps belong behind a search tool instead.

Learn elsewhere

→Tool schemas — next module
→Prompt templates — Prompts

Real Example

Scenario

A Postgres MCP server lists db://schema/public. At session start the client reads it once, so later SQL tools are aimed at real table names.

What you would do

In Model Context Protocol, apply Resources to this scenario: A Postgres MCP server lists db://schema/public. Identify the inputs, run the technique, validate the output, and note one thing you would monitor in production.

Commands

Commands to Remember

list_resources → metadata
read_resource(uri) → text or blob
Resources = read; tools = do
Keep resource payloads small

Cheat Sheet

Quick recap

quick ref

•Resource = readable URI
•list_resources then read_resource
•Nouns vs verbs (tools)
•Do not stuff huge files into context

Common Mistakes

✕Making a write action a resource
✕Returning a 10 MB file as a resource
✕Forgetting a stable URI so the client cannot reload