Sequential Thinking

sequential-thinking

An MCP server that exposes a single sequentialthinking tool for dynamic, reflective, step-by-step problem-solving. It is a Python port of the official TypeScript sequential-thinking MCP server.

This is the first MCP-server plugin in this marketplace — it ships a runnable server instead of a SKILL.md.

What it does

The server registers one tool with the model:

• sequentialthinking — Record one step in an iterative thinking process. The model can record an evolving chain of thoughts, branch off to explore alternatives, revise earlier steps, and adjust the planned thought count on the fly. History is kept in memory for the lifetime of the process.

Once the plugin is enabled, Claude Code namespaces the tool as mcp__plugin_sequential-thinking_sequential-thinking__sequentialthinking (pattern: mcp__plugin_<plugin>_<server>__<tool>). Only a directly-configured (non-plugin) MCP server registers the bare mcp__sequential-thinking__sequentialthinking form.

Tool parameters

Parameter	Type	Description
thought	string	Your current thinking step
nextThoughtNeeded	bool	Whether another thought step is needed
thoughtNumber	int	Current thought number (e.g., 1, 2, 3)
totalThoughts	int	Estimated total thoughts needed
isRevision	bool (optional)	Whether this revises previous thinking
revisesThought	int (optional)	Which thought is being reconsidered
branchFromThought	int (optional)	Branching point thought number
branchId	string (optional)	Branch identifier
needsMoreThoughts	bool (optional)	If more thoughts are needed

Numeric and boolean arguments are also accepted as JSON strings (e.g. "1", "true"), working around clients — including Claude Code — that serialize these values as strings.

Environment variables

• DISABLE_THOUGHT_LOGGING — When set (case-insensitive) to "true", the server suppresses the formatted thought box that is otherwise written to stderr. All other behavior is unchanged.

  For a plugin install, set it by adding an env block to the server entry in the plugin's .mcp.json:

  "env": { "DISABLE_THOUGHT_LOGGING": "true" }
  

Prerequisites

• uv — the server is launched with uv run --script. The script is a PEP 723 inline-dependency script (requires-python >=3.10, mcp>=1.9.4,<2); uv resolves and caches the dependencies automatically on first run. No manual pip install is needed.

How it is wired

The plugin declares the server in .mcp.json:

{
  "mcpServers": {
    "sequential-thinking": {
      "command": "uv",
      "args": ["run", "--no-config", "--script", "${CLAUDE_PLUGIN_ROOT}/scripts/mcp_sequential_thinking.py"]
    }
  }
}

${CLAUDE_PLUGIN_ROOT} is expanded by Claude Code to the installed plugin directory, so the server runs regardless of where the plugin is checked out. --no-config keeps uv from adopting the consuming repo's pyproject.toml/uv.toml (e.g. a private default package index), which would otherwise break dependency resolution when Claude Code is launched from such a directory.