## Purpose

Define the extraction-specific API endpoint — request/response contract, few-shot ChatHistory integration, and tool isolation from the general chat endpoint.

## Requirements

### Requirement: Extraction API endpoint

The API SHALL expose `POST /api/chat/extract` that accepts an `ExtractionRequest` containing the email HTML content and optional follow-up conversation messages. The endpoint SHALL use the few-shot ChatHistory prefix (not the user-editable system prompt) and load extraction-specific SK plugins.

#### Scenario: Initial extraction request

- **WHEN** the client sends a POST to `/api/chat/extract` with email HTML and no follow-up messages
- **THEN** the API assembles the few-shot ChatHistory, appends the email as the final user message, and streams the extraction response via SSE

#### Scenario: Follow-up disambiguation request

- **WHEN** the client sends a POST to `/api/chat/extract` with email HTML and follow-up messages (e.g., user selecting a counterparty)
- **THEN** the API assembles the few-shot ChatHistory, appends the email, appends all follow-up messages, and streams the continuation response via SSE

#### Scenario: SSE streaming contract

- **WHEN** the extraction endpoint streams a response
- **THEN** it uses the same SSE format as `/api/chat`: `data: {"text":"..."}\n\n` for deltas and `data: [DONE]\n\n` for completion

### Requirement: ExtractionRequest DTO

The system SHALL define an `ExtractionRequest` class with `EmailHtml` (string, required) and `Messages` (List<ChatMessage>, optional) for follow-up conversation context.

#### Scenario: First request has email only

- **WHEN** the user uploads an email for the first time
- **THEN** the ExtractionRequest contains `EmailHtml` with the email content and an empty `Messages` list

#### Scenario: Follow-up request includes conversation

- **WHEN** the user replies to a disambiguation question
- **THEN** the ExtractionRequest contains the original `EmailHtml` plus `Messages` with the full assistant/user exchange since the extraction started

### Requirement: Extraction endpoint uses extraction tools only

The extraction endpoint SHALL import only the extraction-specific SK plugins (counterparty lookup, trade validation, currency validation, schema validation). General chat tools (if any) SHALL NOT be loaded for extraction requests.

#### Scenario: Tool isolation

- **WHEN** the extraction endpoint processes a request
- **THEN** only extraction-related KernelFunctions are available to the LLM