> ## Documentation Index > Fetch the complete documentation index at: https://docs.eigenai.com/llms.txt > Use this file to discover all available pages before exploring further. # Function Schema > Understand the function schema format used in EigenData-CLI for defining tool capabilities. A **function schema** is a structured JSON specification that defines a callable function or tool available in your system. EigenData-CLI uses function schemas to understand what tools are available and how to invoke them when generating conversational data. ## Providing Function Schema You can provide function schemas to EigenData-CLI in two ways: ### Option 1: MCP Server If you have a Model Context Protocol (MCP) server, EigenData-CLI can automatically discover available tools: 1. Provide your MCP server URL during setup or via `/configure` 2. The system automatically discovers available tools from the MCP server 3. Function schemas are generated from the tool definitions ``` eigendata> /configure mcp_server_url http://localhost:8080 ``` This approach is ideal when your tools are already defined in an MCP-compatible server. ### Option 2: Local Schema File Provide a local file containing your function definitions: ``` eigendata> /configure schema_file ./my_functions.json ``` Supported file formats: | Format | Extension | Description | | ------ | --------------- | ------------------------------------ | | JSON | `.json` | Array of function objects | | JSONL | `.jsonl` | One function definition per line | | YAML | `.yaml`, `.yml` | YAML-serialized function definitions | ## Schema Format Function schemas follow the OpenAI-style JSON Schema format with four basic fields: ```json theme={null} { "name": "CreateReminder", "description": "Creates a reminder for the user at a specified time.", "parameters": { "type": "object", "properties": { "user_id": { "type": "string", "description": "The ID of the user creating the reminder." }, "title": { "type": "string", "description": "The reminder title, e.g., 'Call mom'." }, "remind_at": { "type": "string", "description": "ISO 8601 datetime for when to trigger the reminder." }, "priority": { "type": "string", "enum": ["low", "medium", "high"], "description": "Priority level of the reminder." } }, "required": ["user_id", "title", "remind_at"], "additionalProperties": false, "examples": [ { "user_id": "user_12345", "title": "Team meeting", "remind_at": "2024-03-15T09:00:00Z", "priority": "high" } ] }, "returns": { "type": "object", "description": "The created reminder object.", "properties": { "reminder_id": { "type": "string", "description": "Unique identifier for the created reminder." }, "status": { "type": "string", "description": "Creation status, either 'created' or 'failed'." } } } } ``` ## Schema Fields | Field | Type | Description | | ------------- | ------ | -------------------------------------------------------------- | | `name` | string | Function identifier (e.g., "create\_reminder", "delete\_task") | | `description` | string | Human-readable explanation of what the function does | | `parameters` | object | JSON Schema object defining input parameters | | `returns` | object | JSON Schema object describing the function's return value | ## Schema File Examples ### Format 1: Standard Array (JSON) The most common format—an array of function objects: ```json theme={null} [ { "name": "CreateReminder", "description": "Creates a reminder for the user.", "parameters": { "type": "object", "properties": { "title": { "type": "string", "description": "The reminder title." }, "remind_at": { "type": "string", "description": "ISO 8601 datetime for the reminder." } }, "required": ["title", "remind_at"] }, "returns": { "type": "object", "description": "The created reminder.", "properties": { "reminder_id": { "type": "string", "description": "Unique identifier for the reminder." } } } }, { "name": "DeleteReminder", "description": "Deletes an existing reminder.", "parameters": { "type": "object", "properties": { "reminder_id": { "type": "string", "description": "The ID of the reminder to delete." } }, "required": ["reminder_id"] }, "returns": { "type": "object", "description": "Deletion result.", "properties": { "success": { "type": "boolean", "description": "Whether the deletion was successful." } } } } ] ``` ### Format 2: YAML with `functions` Wrapper YAML format with an explicit `functions` key: ```yaml theme={null} functions: - name: CreateReminder description: Creates a reminder for the user. parameters: type: object properties: title: type: string description: The reminder title. remind_at: type: string description: ISO 8601 datetime for the reminder. required: - title - remind_at returns: type: object description: The created reminder. properties: reminder_id: type: string description: Unique identifier for the reminder. - name: DeleteReminder description: Deletes an existing reminder. parameters: type: object properties: reminder_id: type: string description: The ID of the reminder to delete. required: - reminder_id returns: type: object description: Deletion result. properties: success: type: boolean description: Whether the deletion was successful. ``` ### Format 3: Extended Format with `tool` and `input_schema` This format uses `tool` as the function identifier and `input_schema` as an object defining parameters with inline metadata: ```json theme={null} [ { "tool": "CreateReminder", "description": "Create a new reminder with a due date/time.", "input_schema": { "name": { "type": "string", "required": true, "description": "Short title for the reminder.", "example": "Replace printer ink cartridge" }, "due": { "type": "string(date-time)", "required": true, "description": "When the reminder is due, in ISO 8601 format.", "example": "2026-02-01T09:00:00" }, "hint": { "type": "string", "required": false, "description": "Optional notes or instructions.", "example": "Check ink levels first." } }, "output_schema": { "reminderId": "string", "name": "string", "due": "string(date-time)", "status": "string(enum: pending|completed)", "error": "object{code:string,message:string}" } }, { "tool": "DeleteReminder", "description": "Delete a reminder by id.", "input_schema": { "reminderId": { "type": "string", "required": true, "description": "Identifier of the reminder to delete.", "example": "rem_12345" } }, "output_schema": { "deleted": "boolean", "reminderId": "string", "error": "object{code:string,message:string}" } } ] ``` | Field | Description | | --------------- | -------------------------------------------------------------------------------- | | `tool` | Function identifier (replaces `name`) | | `input_schema` | Object defining parameters with `type`, `required`, `description`, and `example` | | `output_schema` | Flattened object with field names as keys and type signatures as values | ## Best Practices 1. **Write clear descriptions** - Each function and parameter should have a description that explains its purpose and expected values. 2. **Use specific types** - Use the most specific JSON Schema type for each parameter (`string`, `integer`, `number`, `boolean`, `array`, `object`). 3. **Mark required fields** - Always specify which parameters are required to help generate valid function calls. 4. **Include examples in descriptions** - Add example values in parameter descriptions (e.g., "Email address such as '[user@example.com](mailto:user@example.com)'"). 5. **Define return values** - Always include a `returns` field to document what the function returns. This helps generate realistic tool responses in conversational data. 6. **Use `parameters.examples`** - Provide example parameter objects to demonstrate valid inputs. This improves the quality of generated function calls.