sequential-thinking

Core Concepts / How It Works

The sequential-thinking MCP server provides a single sequentialthinking tool. It forces Claude to explicitly declare thinking steps (thoughts) before generating a response and to proceed through them in order.

Each thinking step consists of the following fields:

Field	Description
thought	Reasoning content for the current step
thoughtNumber	Current step number
totalThoughts	Estimated total number of steps (dynamically adjustable)
nextThoughtNeeded	Whether another step is needed
isRevision	Whether this step revises a previous step
branchFromThought	Step number from which branching begins

Key characteristics:

• Dynamic step count adjustment: totalThoughts can be increased if the problem turns out to be more complex than expected
• Backward revision: Can go back and correct earlier steps if reasoning was wrong
• Branch exploration: Compare multiple approaches in parallel
• Minimum 3 steps recommended: For simple questions, this adds unnecessary overhead

One-Line Summary

An MCP server that breaks down complex problems into sequential thought blocks, improving Claude's reasoning accuracy and transparency.

Getting Started

.claude/settings.json Configuration

{
  "mcpServers": {
    "sequential-thinking": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-sequential-thinking"]
    }
  }
}

Verifying Installation

# After configuring, restart Claude Code and verify the tool is active
# Ask Claude the following:
# "Can you use the sequential thinking tool?"

Claude Desktop (claude_desktop_config.json) Configuration

{
  "mcpServers": {
    "sequential-thinking": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-sequential-thinking"]
    }
  }
}

Prerequisites: Node.js 18+, npx available in the environment.

Practical Example

Scenario: An intermittent 403 error has occurred in the notice creation API of the Next.js 15 "Student Club Notice Board".

Use /mcp sequential-thinking to analyze the following bug step by step:

- Next.js 15 App Router, using Supabase Auth
- Intermittent 403 on POST /api/notices
- Error log: "Row Level Security policy violation"
- Reproduction condition: mainly occurs when posting a notice immediately after login

Claude's sequential thinking flow:

Step 1: Analyze 403 error conditions
 → RLS policy violation + "immediately after login" = suspected timing issue

Step 2: Trace Supabase Auth token passing route
 → Client → API Route → Supabase client order check
 → Timing issue when supabaseServerClient() reads cookie/header?

Step 3: App Router characteristics and session synchronization
 → Session may not have propagated yet after middleware refresh

Step 4: Root cause conclusion (isRevision = false)
 → Route Handler creates Supabase client with old cookie before middleware session refresh completes
 → Fix: After session refresh in middleware, include new token in response headers

Learning Points / Common Pitfalls

• Apply complexity threshold: The effect is most pronounced for problems with 3 or more intertwined conditions. For simple questions, responses will actually be slower.
• Provide step count hints: Giving hints like "analyze this in 5 steps" helps Claude set an appropriate totalThoughts.
• Leverage the revision feature: When a middle step revises a prior step, that point is the key logical branching decision.
• Avoid excessive step counts: Setting more than 10 steps causes a sharp increase in token consumption. 5–7 steps is generally the recommended upper limit.
• Don't ignore the process by looking only at results: The real value of this MCP lies in the intermediate reasoning steps.
• No security risks: This is a pure reasoning structuring tool that does not access the external network or file system.

Related Resources

• investigate (skill) — A similar 4-step root cause analysis skill
• systematic-debugging (skill) — A debugging decision-making framework
• GitHub MCP — MCP for integration
• Fetch MCP — Another popular MCP server

---

Field	Value
Source URL	https://github.com/modelcontextprotocol/servers/tree/main/src/sequentialthinking
Author / Source	Anthropic (Model Context Protocol)
License	MIT
Translation Date	2026-04-12