> ## Documentation Index > Fetch the complete documentation index at: https://docs.yorlet.com/llms.txt > Use this file to discover all available pages before exploring further. # Update a letter template ## OpenAPI ````yaml openapi-core.json POST /v1/letter_templates/{id} openapi: 3.1.0 info: title: Yorlet Core API description: Core platform APIs including buildings, customers, units, and tasks. version: 1.0.0 servers: - url: https://api.yorlet.com description: Production - url: https://api.yorlet.io description: Sandbox security: [] paths: /v1/letter_templates/{id}: post: tags: - Letter templates summary: Update a letter template operationId: letter_templates_update parameters: - schema: type: string description: The id identifier. required: true description: The id identifier. name: id in: path requestBody: content: application/json: schema: type: object properties: address_position: type: string enum: - left - right default: left description: >- Which side of page 1 the recipient address window is printed on. blocks: type: array items: oneOf: - type: object properties: type: type: string enum: - heading content: type: string minLength: 1 description: >- Heading text. Supports the same merge fields as text blocks. required: - type - content - type: object properties: type: type: string enum: - signature file: type: - string - 'null' description: >- File ID of a signature image. When omitted, `name` is printed in a signature style. name: type: - string - 'null' description: >- Name printed under the signature. Defaults to the account name. required: - type - type: object properties: type: type: string enum: - text content: type: string minLength: 1 description: >- Body text. Supports merge fields such as `{{customer.name}}` and `{{owner.address}}`. required: - type - content minItems: 1 description: Ordered content blocks that make up the letter body. description: type: - string - 'null' description: An optional description of when to use this template. name: type: string minLength: 1 description: The name of the letter template. recipient_type: type: string enum: - any - customer - owner default: customer description: >- Who this template is intended for. `any` can be used with either customers or owners. variables: type: array items: type: object properties: key: type: string pattern: ^[a-z][a-z0-9_]*$ description: >- The merge-field key. Interpolated as `{{variables.}}` in heading and text blocks. label: type: string minLength: 1 description: >- A human-readable name shown when filling in this variable. required: - key - label default: [] description: >- Custom variables that can be passed when creating a letter from this template. responses: '200': description: Returns the letter template object if the update succeeded. content: application/json: schema: type: object properties: id: type: string description: Unique identifier for the object. created: type: number description: >- Time at which the object was created. Measured in seconds since the Unix epoch. account: type: string description: >- The account that the object belongs to. Only returned if the request is made with a valid Yorlet-Context header. deleted: type: boolean default: false description: Only returned if the object has been deleted. object: type: string enum: - letter_template address_position: type: string enum: - left - right description: >- Which side of page 1 the recipient address window is printed on. blocks: type: array items: oneOf: - type: object properties: type: type: string enum: - heading content: type: string minLength: 1 description: >- Heading text. Supports the same merge fields as text blocks. required: - type - content - type: object properties: type: type: string enum: - signature file: type: - string - 'null' description: >- File ID of a signature image. When omitted, `name` is printed in a signature style. name: type: - string - 'null' description: >- Name printed under the signature. Defaults to the account name. required: - type - type: object properties: type: type: string enum: - text content: type: string minLength: 1 description: >- Body text. Supports merge fields such as `{{customer.name}}` and `{{owner.address}}`. required: - type - content description: Ordered content blocks that make up the letter body. description: type: - string - 'null' description: An optional description of when to use this template. merge_fields: type: array items: type: string description: >- Merge fields that can be interpolated in heading and text blocks. name: type: string description: The name of the letter template. recipient_type: type: string enum: - any - customer - owner description: >- Who this template is intended for. `any` can be used with either customers or owners. variables: type: array items: type: object properties: key: type: string pattern: ^[a-z][a-z0-9_]*$ description: >- The merge-field key. Interpolated as `{{variables.}}` in heading and text blocks. label: type: string minLength: 1 description: >- A human-readable name shown when filling in this variable. required: - key - label description: >- Custom variables that can be passed when creating a letter from this template. required: - id - created - object - address_position - blocks - description - merge_fields - name - recipient_type - variables security: - ApiKeyAuth: [] components: securitySchemes: ApiKeyAuth: type: apiKey in: header name: Authorization description: API Key authentication. Use "Bearer YOUR_API_KEY". ````