sequential_thinking
Break down complex problems into manageable steps using structured sequential reasoning to analyze, decide, or explore ideas systematically.
Instructions
Engage in systematic step-by-step thinking to analyze complex problems, make decisions, or explore ideas. Each thought builds on the previous ones, creating a chain of reasoning.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| thought | Yes | Your current thought or analysis step | |
| reasoning | No | Optional: Explain why this thought follows from previous ones | |
| category | No | Optional: Categorize this thought (analysis, synthesis, evaluation, etc.) | |
| revise_step | No | Optional: Revise a previous step by its number | |
| branch_from_step | No | Optional: Create a new reasoning branch from a specific step number | |
| target_steps | No | Optional: Target number of thinking steps for this session | |
| complete_thinking | No | Optional: Mark the thinking session as complete |
Implementation Reference
- src/index-backup.ts:103-235 (registration)Registration of the sequential_thinking MCP tool, including description, Zod input schema, and complete inline asynchronous handler function that implements step-by-step thinking logic with state persistence.
server.tool( "sequential_thinking", "Engage in systematic step-by-step thinking to analyze complex problems, make decisions, or explore ideas. Each thought builds on the previous ones, creating a chain of reasoning.", { thought: z.string().describe("Your current thought or analysis step"), reasoning: z.string().optional().describe("Optional: Explain why this thought follows from previous ones"), category: z.string().optional().describe("Optional: Categorize this thought (analysis, synthesis, evaluation, etc.)"), revise_step: z.number().optional().describe("Optional: Revise a previous step by its number"), branch_from_step: z.number().optional().describe("Optional: Create a new reasoning branch from a specific step number"), target_steps: z.number().optional().describe("Optional: Target number of thinking steps for this session"), complete_thinking: z.boolean().optional().describe("Optional: Mark the thinking session as complete") }, async ({ thought, reasoning, category, revise_step, branch_from_step, target_steps, complete_thinking }) => { try { const timestamp = new Date().toISOString(); // Handle revision of existing step if (revise_step !== undefined) { const stepIndex = thinkingSession.currentSteps.findIndex(step => step.id === revise_step); if (stepIndex !== -1) { thinkingSession.currentSteps[stepIndex] = { ...thinkingSession.currentSteps[stepIndex], thought, reasoning, category, timestamp }; } else { return { content: [{ type: "text", text: `❌ Step ${revise_step} not found. Available steps: ${thinkingSession.currentSteps.map(s => s.id).join(', ')}` }] }; } } // Handle branching from existing step else if (branch_from_step !== undefined) { const branchPoint = thinkingSession.currentSteps.find(step => step.id === branch_from_step); if (!branchPoint) { return { content: [{ type: "text", text: `❌ Cannot branch from step ${branch_from_step}. Step not found.` }] }; } // Create new branch thinkingSession.totalSteps++; const newStep: ThinkingStep = { id: thinkingSession.totalSteps, thought: `[Branch from Step ${branch_from_step}] ${thought}`, reasoning, category, timestamp }; thinkingSession.currentSteps.push(newStep); } // Add new step else { thinkingSession.totalSteps++; const newStep: ThinkingStep = { id: thinkingSession.totalSteps, thought, reasoning, category, timestamp }; thinkingSession.currentSteps.push(newStep); } // Handle completion if (complete_thinking) { thinkingSession.isComplete = true; thinkingSession.summary = `Sequential thinking completed with ${thinkingSession.currentSteps.length} steps.`; } // Update target if provided if (target_steps) { thinkingSession.metadata = { ...thinkingSession.metadata, target_steps }; } // Auto-save state await saveThinkingState(); // Generate progress report const progress = target_steps ? ` (${thinkingSession.currentSteps.length}/${target_steps})` : ''; const recentSteps = thinkingSession.currentSteps.slice(-3); let content = `🧠 **Sequential Thinking${progress}**\n\n`; if (revise_step !== undefined) { content += `📝 **Step ${revise_step} Revised**\n\n`; } else if (branch_from_step !== undefined) { content += `🌿 **New Branch from Step ${branch_from_step}**\n\n`; } else { content += `💭 **Step ${thinkingSession.totalSteps} Added**\n\n`; } content += "**Recent Thinking Chain:**\n"; recentSteps.forEach(step => { const categoryLabel = step.category ? ` [${step.category}]` : ''; content += `**${step.id}.${categoryLabel}** ${step.thought}\n`; if (step.reasoning) { content += ` *Reasoning: ${step.reasoning}*\n`; } content += '\n'; }); if (thinkingSession.isComplete) { content += `✅ **Thinking Complete**: ${thinkingSession.summary}\n\n`; } content += `*Continue with next thought or use 'get_thinking_summary' to review all steps*`; return { content: [{ type: "text", text: content }] }; } catch (error) { return { content: [{ type: "text", text: `❌ **Error in sequential thinking**: ${error instanceof Error ? error.message : String(error)}` }] }; } } ); - src/index-backup.ts:115-234 (handler)Core handler logic for the sequential_thinking tool: processes input to add/revise/branch thinking steps, persists session state to JSON file, generates formatted progress reports with recent steps.
async ({ thought, reasoning, category, revise_step, branch_from_step, target_steps, complete_thinking }) => { try { const timestamp = new Date().toISOString(); // Handle revision of existing step if (revise_step !== undefined) { const stepIndex = thinkingSession.currentSteps.findIndex(step => step.id === revise_step); if (stepIndex !== -1) { thinkingSession.currentSteps[stepIndex] = { ...thinkingSession.currentSteps[stepIndex], thought, reasoning, category, timestamp }; } else { return { content: [{ type: "text", text: `❌ Step ${revise_step} not found. Available steps: ${thinkingSession.currentSteps.map(s => s.id).join(', ')}` }] }; } } // Handle branching from existing step else if (branch_from_step !== undefined) { const branchPoint = thinkingSession.currentSteps.find(step => step.id === branch_from_step); if (!branchPoint) { return { content: [{ type: "text", text: `❌ Cannot branch from step ${branch_from_step}. Step not found.` }] }; } // Create new branch thinkingSession.totalSteps++; const newStep: ThinkingStep = { id: thinkingSession.totalSteps, thought: `[Branch from Step ${branch_from_step}] ${thought}`, reasoning, category, timestamp }; thinkingSession.currentSteps.push(newStep); } // Add new step else { thinkingSession.totalSteps++; const newStep: ThinkingStep = { id: thinkingSession.totalSteps, thought, reasoning, category, timestamp }; thinkingSession.currentSteps.push(newStep); } // Handle completion if (complete_thinking) { thinkingSession.isComplete = true; thinkingSession.summary = `Sequential thinking completed with ${thinkingSession.currentSteps.length} steps.`; } // Update target if provided if (target_steps) { thinkingSession.metadata = { ...thinkingSession.metadata, target_steps }; } // Auto-save state await saveThinkingState(); // Generate progress report const progress = target_steps ? ` (${thinkingSession.currentSteps.length}/${target_steps})` : ''; const recentSteps = thinkingSession.currentSteps.slice(-3); let content = `🧠 **Sequential Thinking${progress}**\n\n`; if (revise_step !== undefined) { content += `📝 **Step ${revise_step} Revised**\n\n`; } else if (branch_from_step !== undefined) { content += `🌿 **New Branch from Step ${branch_from_step}**\n\n`; } else { content += `💭 **Step ${thinkingSession.totalSteps} Added**\n\n`; } content += "**Recent Thinking Chain:**\n"; recentSteps.forEach(step => { const categoryLabel = step.category ? ` [${step.category}]` : ''; content += `**${step.id}.${categoryLabel}** ${step.thought}\n`; if (step.reasoning) { content += ` *Reasoning: ${step.reasoning}*\n`; } content += '\n'; }); if (thinkingSession.isComplete) { content += `✅ **Thinking Complete**: ${thinkingSession.summary}\n\n`; } content += `*Continue with next thought or use 'get_thinking_summary' to review all steps*`; return { content: [{ type: "text", text: content }] }; } catch (error) { return { content: [{ type: "text", text: `❌ **Error in sequential thinking**: ${error instanceof Error ? error.message : String(error)}` }] }; } } - src/index-backup.ts:106-113 (schema)Zod schema defining input parameters for the sequential_thinking tool.
{ thought: z.string().describe("Your current thought or analysis step"), reasoning: z.string().optional().describe("Optional: Explain why this thought follows from previous ones"), category: z.string().optional().describe("Optional: Categorize this thought (analysis, synthesis, evaluation, etc.)"), revise_step: z.number().optional().describe("Optional: Revise a previous step by its number"), branch_from_step: z.number().optional().describe("Optional: Create a new reasoning branch from a specific step number"), target_steps: z.number().optional().describe("Optional: Target number of thinking steps for this session"), complete_thinking: z.boolean().optional().describe("Optional: Mark the thinking session as complete") - src/index-backup.ts:37-62 (helper)TypeScript interfaces defining ThinkingStep and ThinkingSession structures used by the sequential_thinking tool for state management.
interface ThinkingStep { id: number; thought: string; reasoning?: string; timestamp: string; category?: string; } interface ThinkingSession { currentSteps: ThinkingStep[]; totalSteps: number; isComplete: boolean; summary?: string; metadata?: Record<string, any>; pdfContext?: { filename?: string; content?: string; metadata?: Record<string, any>; }; } let thinkingSession: ThinkingSession = { currentSteps: [], totalSteps: 0, isComplete: false }; - src/index-backup.ts:64-88 (helper)Persistent storage helper functions for saving and loading the thinking session state to/from a JSON file in user home directory.
const STORAGE_FILE = path.join(os.homedir(), '.mcp-sequential-thinking.json'); async function initializeStorage() { try { const data = await fs.readFile(STORAGE_FILE, 'utf-8'); const saved = JSON.parse(data); thinkingSession = { ...thinkingSession, ...saved }; console.error(`LOADED: thinking state: ${thinkingSession.currentSteps.length} steps`); } catch (error) { console.error("INIT: Starting with fresh thinking state"); } } async function saveThinkingState() { try { await fs.writeFile(STORAGE_FILE, JSON.stringify(thinkingSession, null, 2)); } catch (error) { console.error("⚠️ Failed to save thinking state:", error); } } async function loadThinkingState() { return thinkingSession; }