MCP Think Tool

think

Append thoughts to a reasoning log for complex problem-solving, enabling structured analysis without external data retrieval.

Instructions

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.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`thought`	Yes	A thought to think about.

Implementation Reference

src/index.ts:18-29 (handler)

Handler function for the 'think' tool. Takes a 'thought' parameter and returns it as a text content block in the response, effectively echoing the thought without performing any other actions.

async ({ thought }) => {
  // This tool does nothing at all - it's a no-op
  // It simply lets Claude externalize its thinking process
  return {
    content: [
      {
        type: "text",
        text: thought,
      },
    ],
  };
}

src/index.ts:15-17 (schema)
Input schema for the 'think' tool using Zod: defines 'thought' as a required string.
```
{
  thought: z.string().describe("A thought to think about."),
},
```

src/index.ts:12-30 (registration)

Registers the 'think' tool on the MCP server with name, description, input schema, and handler function.

server.tool(
  "think",
  "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.",
  {
    thought: z.string().describe("A thought to think about."),
  },
  async ({ thought }) => {
    // This tool does nothing at all - it's a no-op
    // It simply lets Claude externalize its thinking process
    return {
      content: [
        {
          type: "text",
          text: thought,
        },
      ],
    };
  }
);

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 15, 2025

TDQS

A3.9/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It effectively describes key traits: 'It will not obtain new information or change the database' clarifies it's a read-only, non-destructive operation, and 'just append the thought to the log' explains the action. This covers safety and basic behavior, though it could add details like log format or persistence.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is appropriately sized with two sentences that efficiently convey purpose and usage. It is front-loaded with the core action and avoids unnecessary details. Every sentence adds value, though minor improvements in clarity could enhance conciseness further.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's low complexity (one parameter, no annotations, no output schema), the description is reasonably complete. It covers purpose, usage, and behavioral traits adequately. However, it could be more specific about what 'think' involves or the log's nature, which would improve completeness for an agent's understanding.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 100% description coverage, with the 'thought' parameter documented as 'A thought to think about.' The description adds no additional parameter semantics beyond this, such as format or constraints. Given the high schema coverage, a baseline score of 3 is appropriate, as the schema already provides adequate parameter information.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Use the tool to think about something' and 'append the thought to the log.' It specifies the verb ('think') and resource ('thought log'), though it doesn't distinguish from siblings since none exist. The purpose is clear but could be more specific about what 'think' entails operationally.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit guidance on when to use the tool: 'Use it when complex reasoning or some cache memory is needed.' This gives clear context for its application. However, it lacks exclusions or alternatives, which is acceptable since no sibling tools are present to differentiate from.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server

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