# Directory Structure
```
├── .gitignore
├── package.json
├── README.md
├── src
│ └── index.ts
└── tsconfig.json
```
# Files
--------------------------------------------------------------------------------
/.gitignore:
--------------------------------------------------------------------------------
```
1 | # Dependencies
2 | node_modules/
3 | npm-debug.log
4 | yarn-debug.log
5 | yarn-error.log
6 | package-lock.json
7 | yarn.lock
8 |
9 | # Build outputs
10 | build/
11 | dist/
12 | *.tsbuildinfo
13 |
14 | # TypeScript incremental compilation cache
15 | *.tsbuildinfo
16 |
17 | # Environment variables
18 | .env
19 | .env.local
20 | .env.*.local
21 |
22 | # IDE/Editor folders
23 | .idea/
24 | .vscode/
25 | *.swp
26 | *.swo
27 | .DS_Store
28 |
29 | # Logs
30 | logs/
31 | *.log
32 |
33 | # Operating System Files
34 | .DS_Store
35 | Thumbs.db
36 |
```
--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
```markdown
1 | # MCP Think Tool
2 |
3 | This is an implementation of the "Think Tool" described in Anthropic's engineering blog post as an MCP server. The Think Tool is a simple but effective prompt engineering technique that helps Claude break down complex problems and enhance its reasoning capabilities.
4 |
5 | ## How it Works
6 |
7 | The Think Tool is incredibly simple - it provides a no-op tool that does nothing except echo back the input. The magic is in how it allows Claude to:
8 |
9 | 1. Take a step back and think through complex problems
10 | 2. Break down reasoning into discrete steps
11 | 3. Organize thoughts more systematically
12 | 4. Cache intermediate results during complex calculations
13 | 5. Show its work when solving problems
14 |
15 | As described by Anthropic, this is a "prompt engineering trick" where they use the standard tool calling mechanism to define a tool called "think" that "does nothing at all" - there is no implementation - it simply allows the model to use its existing training about when to use tools to stop and dump additional thoughts into the context.
16 |
17 | ## Implementation Details
18 |
19 | The MCP server exposes a single tool:
20 |
21 | 1. `think` - Takes a thought as input and returns it
22 |
23 | Tool definition:
24 |
25 | ```json
26 | {
27 | "name": "think",
28 | "description": "Use the tool to think about something. It will not obtain new information or change the database, but just append the thought to the log. Use it when complex reasoning or some cache memory is needed.",
29 | "input_schema": {
30 | "type": "object",
31 | "properties": {
32 | "thought": {
33 | "type": "string",
34 | "description": "A thought to think about."
35 | }
36 | },
37 | "required": ["thought"]
38 | }
39 | }
40 | ```
41 |
42 | ## Usage
43 |
44 | ### Setup
45 |
46 | 1. Clone this repository
47 | 2. Run `npm install` to install dependencies
48 | 3. Run `npm run build` to compile TypeScript
49 | 4. Run `npm start` to start the MCP server
50 |
51 | ### Connecting to Claude Desktop
52 |
53 | Add this server to your Claude Desktop configuration file:
54 |
55 | ```json
56 | {
57 | "mcpServers": {
58 | "think-tool": {
59 | "command": "node",
60 | "args": ["/path/to/mcp-think-tool/build/index.js"]
61 | }
62 | }
63 | }
64 | ```
65 |
66 | Add this prompt to teach the LLM how to use the think tool:
67 |
68 | ```
69 | ## Using the think tool
70 |
71 | Before taking any action or responding to the user after receiving tool results, use the think tool as a scratchpad to:
72 | - List the specific rules that apply to the current request
73 | - Check if all required information is collected
74 | - Verify that the planned action complies with all policies
75 | - Iterate over tool results for correctness
76 |
77 | Here are some examples of what to iterate over inside the think tool:
78 | <think_tool_example_1>
79 | User wants to cancel flight ABC123
80 | - Need to verify: user ID, reservation ID, reason
81 | - Check cancellation rules:
82 | * Is it within 24h of booking?
83 | * If not, check ticket class and insurance
84 | - Verify no segments flown or are in the past
85 | - Plan: collect missing info, verify rules, get confirmation
86 | </think_tool_example_1>
87 |
88 | <think_tool_example_2>
89 | User wants to book 3 tickets to NYC with 2 checked bags each
90 | - Need user ID to check:
91 | * Membership tier for baggage allowance
92 | * Which payments methods exist in profile
93 | - Baggage calculation:
94 | * Economy class × 3 passengers
95 | * If regular member: 1 free bag each → 3 extra bags = $150
96 | * If silver member: 2 free bags each → 0 extra bags = $0
97 | * If gold member: 3 free bags each → 0 extra bags = $0
98 | - Payment rules to verify:
99 | * Max 1 travel certificate, 1 credit card, 3 gift cards
100 | * All payment methods must be in profile
101 | * Travel certificate remainder goes to waste
102 | - Plan:
103 | 1. Get user ID
104 | 2. Verify membership level for bag fees
105 | 3. Check which payment methods in profile and if their combination is allowed
106 | 4. Calculate total: ticket price + any bag fees
107 | 5. Get explicit confirmation for booking
108 | </think_tool_example_2>
109 | ```
110 |
111 | Replace `/path/to/mcp-think-tool` with the actual path to this repository.
112 |
113 | ## Examples
114 |
115 | Claude might use the Think Tool to work through a problem like:
116 |
117 | ```
118 | Solving 235 × 47:
119 |
120 | Think: First I'll break this down. I need to multiply 235 by 47.
121 | Think: I'll start by calculating 235 × 40 = 9,400
122 | Think: Then I'll calculate 235 × 7 = 1,645
123 | Think: Now I add them together: 9,400 + 1,645 = 11,045
124 |
125 | Therefore, 235 × 47 = 11,045
126 | ```
127 |
128 | Or for a more complex reasoning task:
129 |
130 | ```
131 | Think: I need to analyze the given problem carefully. The question asks about the impact of reducing carbon emissions by 15% over 5 years.
132 | Think: First, I should establish the baseline emissions. The document mentions current annual emissions of 50 million metric tons.
133 | Think: 15% reduction over 5 years means approximately 3% reduction per year, assuming linear decrease.
134 | Think: After 5 years, annual emissions would be 50 × (1 - 0.15) = 50 × 0.85 = 42.5 million metric tons.
135 | Think: The total reduction over 5 years would be the sum of the reductions each year...
136 | ```
137 |
138 | ## Development
139 |
140 | - `src/index.ts` - MCP server implementation
141 |
142 | ## License
143 |
144 | ISC
145 |
```
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/tsconfig.json:
--------------------------------------------------------------------------------
```json
1 | {
2 | "compilerOptions": {
3 | "target": "ES2022",
4 | "module": "Node16",
5 | "moduleResolution": "Node16",
6 | "outDir": "./build",
7 | "rootDir": "./src",
8 | "strict": true,
9 | "esModuleInterop": true,
10 | "skipLibCheck": true,
11 | "forceConsistentCasingInFileNames": true
12 | },
13 | "include": [
14 | "src/**/*"
15 | ],
16 | "exclude": [
17 | "node_modules"
18 | ]
19 | }
20 |
```
--------------------------------------------------------------------------------
/package.json:
--------------------------------------------------------------------------------
```json
1 | {
2 | "name": "mcp-think-tool",
3 | "version": "1.0.0",
4 | "description": "A basic MCP server for memory management",
5 | "main": "build/index.js",
6 | "type": "module",
7 | "scripts": {
8 | "build": "tsc",
9 | "start": "node build/index.js",
10 | "dev": "tsc && node build/index.js",
11 | "test": "echo \"Error: no test specified\" && exit 1"
12 | },
13 | "keywords": [
14 | "mcp",
15 | "llm",
16 | "memory"
17 | ],
18 | "author": "",
19 | "license": "ISC",
20 | "dependencies": {
21 | "@modelcontextprotocol/sdk": "^1.7.0",
22 | "zod": "^3.22.4"
23 | },
24 | "devDependencies": {
25 | "@types/node": "^20.11.0",
26 | "typescript": "^5.3.3"
27 | }
28 | }
29 |
```
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/src/index.ts:
--------------------------------------------------------------------------------
```typescript
1 | import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
2 | import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
3 | import { z } from "zod";
4 |
5 | // Create server instance
6 | const server = new McpServer({
7 | name: "mcp-think-tool",
8 | version: "1.0.0",
9 | });
10 |
11 | // Register the "think" tool
12 | server.tool(
13 | "think",
14 | "Use the tool to think about something. It will not obtain new information or change the database, but just append the thought to the log. Use it when complex reasoning or some cache memory is needed.",
15 | {
16 | thought: z.string().describe("A thought to think about."),
17 | },
18 | async ({ thought }) => {
19 | // This tool does nothing at all - it's a no-op
20 | // It simply lets Claude externalize its thinking process
21 | return {
22 | content: [
23 | {
24 | type: "text",
25 | text: thought,
26 | },
27 | ],
28 | };
29 | }
30 | );
31 |
32 | async function main() {
33 | const transport = new StdioServerTransport();
34 | await server.connect(transport);
35 | console.error("MCP Think Tool Server running on stdio");
36 | }
37 |
38 | main().catch((error) => {
39 | console.error("Fatal error in main():", error);
40 | process.exit(1);
41 | });
42 |
```