Calculator MCP Server

subtract

Calculate the difference between two numbers by subtracting the second from the first, returning the result as a string.

Instructions

Subtract the second number from the first.

Args: a: The number to subtract from. b: The number to subtract.

Returns: A string with the result of a - b.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "a": "<a>",
      "b": "<b>"
    },
    "name": "subtract"
  }
}

Input Schema

Name	Required	Description	Default
`a`	Yes
`b`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 8, 2026

TDQS

A4.4/5.0

Behavior4/5

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

With no annotations provided, the description carries the burden of explaining behavior. It clearly states that the operation subtracts b from a and that the result is returned as a string, which covers the primary behavioral contract. It does not mention potential edge cases, but for simple numeric subtraction this is acceptable.

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

Conciseness5/5

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

The description is short, direct, and free of unnecessary wording. Every line serves a purpose, with argument details and return behavior clearly separated.

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

Completeness5/5

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

For a simple arithmetic tool, the description provides all necessary context: what operation is performed, which argument is which, and what the return type is. No additional edge-case handling or output schema explanation is required for typical use.

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

Parameters5/5

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

The schema only provides types and titles for a and b, but the description adds crucial meaning: 'a' is the number to subtract from, and 'b' is the number to subtract. This clarifies the order-dependent semantics fully.

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

Purpose5/5

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

The description clearly states the operation: subtract the second number from the first. It uses a specific verb and resource, and the behavior is distinct from sibling arithmetic tools like add, multiply, divide, and power.

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

Usage Guidelines3/5

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

The description implies when to use the tool—when a difference between two numbers is needed—but does not explicitly state when to prefer it over alternatives. There is no direct comparison or exclusion of sibling tools, leaving usage guidance somewhat implicit.

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

Deploy Server