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MCP Tool Definition Builder — Input and Output Schemas

Prepare the JSON metadata for one MCP tool with flat input and output fields. This builder creates the definition you can integrate into a server; it does not implement or call the tool.

Calculations run in your browser. No account or API key is needed.

Make it yours

An editable example is loaded below.

Up to 30 flat fields. Use [] for no arguments. required defaults to true.

Your result

Input fields
2
Output fields
2
{
  "name": "convert_temperature",
  "title": "Temperature converter",
  "description": "Convert a temperature between Celsius and Fahrenheit.",
  "inputSchema": {
    "type": "object",
    "properties": {
      "value": {
        "type": "number",
        "description": "Temperature to convert"
      },
      "from": {
        "type": "string",
        "enum": [
          "C",
          "F"
        ]
      }
    },
    "required": [
      "value",
      "from"
    ],
    "additionalProperties": false
  },
  "outputSchema": {
    "type": "object",
    "properties": {
      "value": {
        "type": "number"
      },
      "unit": {
        "type": "string",
        "enum": [
          "C",
          "F"
        ]
      }
    },
    "required": [
      "value",
      "unit"
    ],
    "additionalProperties": false
  }
}

How to use this tool

  1. Enter a unique tool name and describe the operation it performs.

  2. Edit the JSON parameter lists using name, type, description, required and optional enum.

  3. Copy the definition into your server project and implement matching validation and behavior.

Make the contract explicit

Supported field types are string, number, integer and boolean. Parameters default to required; set required to false for optional fields. An enum restricts a field to listed values of the same type. Each generated object rejects undeclared properties. Use an empty input list for a tool with no arguments.

Connect metadata to implementation

The result is one tool entry, not a complete tools/list response or server configuration. An output list produces outputSchema; leave it blank to omit that field. Your handler still needs to return matching structured data. Nested objects, references, transport setup and authentication belong in your server implementation.

Common questions

Which tool names are accepted?

Use 1–128 ASCII letters, digits, underscores, hyphens or dots. Names are case-sensitive and should be unique within your server.

Is a parameter list a JSON Schema?

No. It is this builder’s compact input format. The generated inputSchema and optional outputSchema use JSON Schema object definitions.