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Dictionary

MCP Tools

MCP tools are typed, described functions an AI model can call — the unit of capability that decides whether an agent is useful or dangerous.

1 min readupdated 2026-08-01

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Each MCP tool has a name, a description, a JSON-schema input and annotations (read-only, destructive, idempotent). The model chooses tools from those descriptions alone, so tool design is prompt design: narrow scope, unambiguous names, small inputs and compact outputs. Write tools should carry approval requirements.

MCP tools are typed, described functions an AI model can call — the unit of capability that decides whether an agent is useful or dangerous. Each MCP tool has a name, a description, a JSON-schema input and annotations (read-only, destructive, idempotent). The model chooses tools from those descriptions alone, so tool design is prompt design: narrow scope, unambiguous names, small inputs and compact outputs. Write tools should carry approval requirements. In practice: `search_orders(customer_email, status)` returning 10 compact rows beats a generic `run_sql(query)` tool that hands the model the whole database.
Definition
Each MCP tool has a name, a description, a JSON-schema input and annotations (read-only, destructive, idempotent). The model chooses tools from those descriptions alone, so tool design is prompt design: narrow scope, unambiguous names, small inputs and compact outputs. Write tools should carry approval requirements.
Example
`search_orders(customer_email, status)` returning 10 compact rows beats a generic `run_sql(query)` tool that hands the model the whole database.
Related Workflows
Related Tool Stacks
Related Prompts

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What is MCP Tools?

Each MCP tool has a name, a description, a JSON-schema input and annotations (read-only, destructive, idempotent). The model chooses tools from those descriptions alone, so tool design is prompt design: narrow scope, unambiguous names, small inputs and compact outputs. Write tools should carry approval requirements.

What is an example of MCP Tools?

`search_orders(customer_email, status)` returning 10 compact rows beats a generic `run_sql(query)` tool that hands the model the whole database.

Why does MCP Tools matter?

MCP tools are typed, described functions an AI model can call — the unit of capability that decides whether an agent is useful or dangerous.

What should I learn after MCP Tools?

Open the related workflows and prompts further down this page: they show how this idea is applied in a real task, step by step.

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Related concepts

The vocabulary this page depends on.

  • →MCP (Model Context Protocol)

    Open standard letting AI clients call external tools, data and prompts.

  • →MCP Server

    An MCP server exposes tools, resources and prompts from one system so any MCP-compatible AI client can use them over a standard protocol.

  • →MCP Client

    An MCP client is the AI-side host that discovers servers, lists their tools and routes the model's calls to them.

  • →MCP Resources

    MCP resources are addressable read-only context — files, records, docs — that a client can pull into the model instead of calling a tool.

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Related workflows

Turn this into a repeatable process.

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Related tool stacks

The tools that run it in production.

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Related prompts

Reusable prompts for this job.

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Comparisons & alternatives

Pick between the options.

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