> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fincept.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Calculate Twist Sensitivity (Steepening/Flattening)

> Measures sensitivity to yield curve steepening or flattening - short rates decrease while long rates increase (steepening) or vice versa (flattening). Critical for curve trades, butterfly strategies, and understanding non-parallel curve movements that often occur during policy transitions. [Tier: PRO, Credits: 5]



## OpenAPI

````yaml api-specs/risk.json post /quantlib/risk/sensitivities/twist
openapi: 3.1.0
info:
  title: FinceptQuantLib API - Risk Module
  description: >-
    Professional-grade risk management endpoints including Value at Risk (VaR),
    stress testing, copulas, extreme value theory (EVT), XVA calculations,
    sensitivities, and portfolio hedging. Part of the Pro Tier (5 credits per
    request).
  version: 3.0.0
  contact:
    name: Fincept API Support
    url: https://fincept.in
    email: support@fincept.in
servers:
  - url: https://api.fincept.in
    description: Fincept API Production Server
security:
  - APIKeyHeader: []
tags:
  - name: quantlib-risk
    description: Risk Management Module - Pro Tier (5 credits/request)
    x-displayName: Risk
paths:
  /quantlib/risk/sensitivities/twist:
    post:
      tags:
        - quantlib-risk
      summary: Calculate Twist Sensitivity (Steepening/Flattening)
      description: >-
        Measures sensitivity to yield curve steepening or flattening - short
        rates decrease while long rates increase (steepening) or vice versa
        (flattening). Critical for curve trades, butterfly strategies, and
        understanding non-parallel curve movements that often occur during
        policy transitions. [Tier: PRO, Credits: 5]
      operationId: twist_sens
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - cashflows
                - times
                - curve_rates
              properties:
                cashflows:
                  type: array
                  description: Cashflows to value
                  items:
                    type: number
                  example:
                    - 5
                    - 5
                    - 5
                    - 105
                times:
                  type: array
                  description: Time points in years
                  items:
                    type: number
                  example:
                    - 1
                    - 2
                    - 3
                    - 4
                curve_rates:
                  type: array
                  description: Current discount rates
                  items:
                    type: number
                  example:
                    - 0.02
                    - 0.025
                    - 0.03
                    - 0.035
                bump_size:
                  type: number
                  description: Twist amount
                  example: 0.0001
                  default: 0.0001
            example:
              cashflows:
                - 40
                - 40
                - 40
                - 40
                - 1040
              times:
                - 1
                - 2
                - 3
                - 4
                - 5
              curve_rates:
                - 0.015
                - 0.02
                - 0.025
                - 0.028
                - 0.03
              bump_size: 0.0001
      responses:
        '200':
          description: Twist sensitivity
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: true
                  data:
                    type: object
                    properties:
                      twist_sensitivity:
                        type: number
                        description: Sensitivity to curve steepening/flattening
                        example: -185.25
              example:
                success: true
                data:
                  twist_sensitivity: -185.25
        '401':
          $ref: '#/components/responses/UnauthorizedError'
        '402':
          $ref: '#/components/responses/InsufficientCreditsError'
        '422':
          $ref: '#/components/responses/ValidationError'
components:
  responses:
    UnauthorizedError:
      description: Authentication information is missing or invalid
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: string
                example: Invalid API key
    InsufficientCreditsError:
      description: Insufficient API credits for this request
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: string
                example: Insufficient credits. This endpoint requires 5 credits.
    ValidationError:
      description: Request validation error
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: array
                items:
                  type: object
                  properties:
                    loc:
                      type: array
                      items:
                        type: string
                    msg:
                      type: string
                    type:
                      type: string
  securitySchemes:
    APIKeyHeader:
      type: apiKey
      in: header
      name: X-API-Key
      description: >-
        API key for authentication. Get your key at
        https://api.fincept.in/auth/register

````