Step 4 of 5

Tool config

Name your tool, write the LLM-facing description, and define the input/output schemas. The description is the primary signal the model uses when deciding whether to call this tool.

Tool identity

Machine-readable name and LLM-facing description

Tool name required

Machine-readable identifier used in MCP tool calls. Only lowercase letters, numbers and underscores. Cannot be changed after publishing.

Display name required

Human-readable name shown in the console and audit log.

Tool title (optional)

Short imperative sentence shown in the MCP tool manifest.

Description required

LLM-facing description. Be precise — this is the primary signal the model uses to decide whether to invoke this tool.

Writing effective descriptions

Start with a verb ("Creates", "Fetches", "Updates"). Mention key input requirements. Describe what a successful response looks like. Avoid vague phrasing like "handles" or "manages". See description best practices →

Input schema

Parameters the LLM passes when calling this tool

JSON Schema draft-07

json / input-schema
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "required": ["first_name", "last_name", "email"],
  "properties": {
    "first_name": { "type": "string", "description": "Contact first name" },
    "last_name":  { "type": "string", "description": "Contact last name" },
    "email":      { "type": "string", "format": "email", "description": "Primary contact email address" },
    "company":    { "type": "string", "description": "Company or organisation name" },
    "phone":      { "type": "string", "description": "Phone number in E.164 format" },
    "source":     { "type": "string", "enum": ["web","api","import"], "default": "api" }
  },
  "additionalProperties": false
}

Output schema

Shape of the data returned to the LLM after a successful call

JSON Schema draft-07

json / output-schema
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "lead_id":    { "type": "string", "description": "Unique identifier of the created lead" },
    "status":     { "type": "string", "description": "Initial lead status assigned by the CRM" },
    "created_at": { "type": "string", "format": "date-time" },
    "owner_id":   { "type": "string", "description": "CRM user ID of the assigned owner" }
  }
}

Schemas are protocol-agnostic

These schemas describe the MCP contract, not the upstream wire format. Field mapping in Step 5 translates between the two. You can upload a sample JSON response to auto-generate the output schema.