## ADDED Requirements

### Requirement: Counterparty lookup tool

The extraction plugin SHALL expose a `lookup_counterparty` Semantic Kernel function that accepts a counterparty name string and calls the external counterparty API. The tool SHALL return a list of candidate (counterparty, legal_entity) tuples.

#### Scenario: Single match found

- **WHEN** the tool is called with a counterparty name that matches exactly one record
- **THEN** the tool returns a single candidate with the counterparty name and legal entity ID

#### Scenario: Multiple matches found (disambiguation needed)

- **WHEN** the tool is called with a counterparty name that matches multiple records
- **THEN** the tool returns all matching candidates so the agent can present them to the user for selection

#### Scenario: No match found

- **WHEN** the tool is called with a counterparty name that matches no records
- **THEN** the tool returns an empty list and an informative message so the agent can ask the user for clarification

### Requirement: Trade validation tool

The extraction plugin SHALL expose a `validate_trade` Semantic Kernel function that accepts a trade ID and calls the external trade validation API to verify the trade exists.

#### Scenario: Valid trade ID

- **WHEN** the tool is called with a known trade ID
- **THEN** the tool returns a success result confirming the trade exists

#### Scenario: Invalid trade ID

- **WHEN** the tool is called with an unknown trade ID
- **THEN** the tool returns an error result so the agent can flag it to the user

### Requirement: Currency validation tool

The extraction plugin SHALL expose a `validate_currency` Semantic Kernel function that accepts a currency code and calls the external currency validation API to verify it is a valid ISO currency code.

#### Scenario: Valid currency code

- **WHEN** the tool is called with "GBP"
- **THEN** the tool returns a success result

#### Scenario: Invalid currency code

- **WHEN** the tool is called with an unrecognized code
- **THEN** the tool returns an error with suggestions for valid codes

### Requirement: Schema validation tool

The extraction plugin SHALL expose a `validate_schema` Semantic Kernel function that accepts the full ExtractionResult JSON and validates that all required fields are present and correctly typed for every TradeItem.

#### Scenario: Valid extraction result

- **WHEN** the tool is called with a complete and correctly typed ExtractionResult JSON
- **THEN** the tool returns a success result with no errors

#### Scenario: Missing required fields

- **WHEN** the tool is called with a TradeItem missing the `trade_id` field
- **THEN** the tool returns a failure result listing the missing fields and which item they belong to

### Requirement: External API configuration

All external API base URLs SHALL be configurable via `appsettings.json` under an `ExternalApis` section. Each tool's HttpClient SHALL read its base URL from configuration at startup.

#### Scenario: Configuration at startup

- **WHEN** the API starts
- **THEN** it reads external API base URLs from the `ExternalApis` configuration section and configures typed HttpClients accordingly

### Requirement: External API error handling

Each tool SHALL handle HTTP errors from external APIs gracefully, returning a structured error message that the LLM agent can reason about rather than throwing exceptions.

#### Scenario: External API unavailable

- **WHEN** a tool calls an external API that is unreachable
- **THEN** the tool returns an error result with a descriptive message (e.g., "Counterparty API unavailable") so the agent can inform the user