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

> ## Agent Instructions
> Every Lath operation is POST https://platform.trylath.com/<operation name with dots replaced by slashes>, with a JSON body and `Authorization: Bearer <key>`. `email.send` is POST /email/send.
> Branch on `error.code`, never on `error.message`. Every refusal also carries `error.fix`, which names the next step.
> Send an `Idempotency-Key` header on any operation that is not retry-safe, so a retry cannot run it twice.
> A `lath_test_` key emails only the account's own members and sends no SMS; a `lath_live_` key reaches real recipients and is billed.
> The OpenAPI document, generated from the same registry as the routes, is at https://platform.trylath.com/openapi.json.

# sms.template.set

> Saves a new draft version of a named SMS template: one body with {{variables}}, {{#if}} and {{#each}}. Give a `locale` to write that language's variant; each language has its own versions and publishes on its own. Refuses syntax errors with line numbers. Reports the segment count the body will cost, since that is what a message is billed by and it is decided by the wording — and a translation is very often the one that crosses into a second segment. Nothing is sent from a draft until sms.template.publish.



## OpenAPI

````yaml /api-reference/openapi.json post /sms/template/set
openapi: 3.1.0
info:
  title: Lath API
  version: 0.1.0
  description: >-
    Every operation is one POST. The same set is reachable over MCP, the SDK and
    the CLI; nothing is dashboard-only.
servers:
  - url: https://platform.trylath.com
    description: This deployment
security: []
paths:
  /sms/template/set:
    post:
      tags:
        - sms
      summary: sms.template.set
      description: >-
        Saves a new draft version of a named SMS template: one body with
        {{variables}}, {{#if}} and {{#each}}. Give a `locale` to write that
        language's variant; each language has its own versions and publishes on
        its own. Refuses syntax errors with line numbers. Reports the segment
        count the body will cost, since that is what a message is billed by and
        it is decided by the wording — and a translation is very often the one
        that crosses into a second segment. Nothing is sent from a draft until
        sms.template.publish.
      operationId: sms.template.set
      parameters:
        - name: Idempotency-Key
          in: header
          required: false
          schema:
            type: string
          description: >-
            Replays the stored response for the same key and input; refuses
            different input.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $schema: https://json-schema.org/draft/2020-12/schema
              type: object
              properties:
                name:
                  type: string
                  minLength: 1
                  maxLength: 120
                  pattern: ^[a-z][a-z0-9_-]*(\.[a-z][a-z0-9_-]*)*$
                  description: >-
                    The template name. The reserved name auth.signin.sms
                    overrides the built-in sign-in text.
                locale:
                  description: >-
                    Language variant, e.g. 'fr' or 'pt-BR'. Omit for the default
                    variant used when nothing more specific fits the recipient.
                  type: string
                  maxLength: 20
                text:
                  type: string
                  minLength: 1
                  maxLength: 1600
                  description: The message body; may reference {{variables}}
              required:
                - name
                - text
              additionalProperties: false
      responses:
        '200':
          description: '{ activityId, result }. activityId is empty for reads.'
          content:
            application/json:
              schema:
                type: object
                properties:
                  activityId:
                    type: string
                    description: The activity this call created, or empty for a read.
                  result:
                    $schema: https://json-schema.org/draft/2020-12/schema
                    type: object
                    properties:
                      name:
                        type: string
                      draft: {}
                      segments:
                        type: integer
                        minimum: -9007199254740991
                        maximum: 9007199254740991
                      encoding:
                        type: string
                      units:
                        type: integer
                        minimum: -9007199254740991
                        maximum: 9007199254740991
                      reserved:
                        type: boolean
                    required:
                      - name
                      - draft
                      - segments
                      - encoding
                      - units
                      - reserved
                    additionalProperties: {}
                required:
                  - activityId
                  - result
        '400':
          description: invalid_input or invalid_json
        '401':
          description: unauthenticated
        '403':
          description: forbidden
        '404':
          description: not_found
        '409':
          description: 'conflict: idempotency_mismatch, email_taken, last_key'
        '413':
          description: body_too_large
        '429':
          description: rate_limited
      security:
        - bearer: []
components:
  securitySchemes:
    bearer:
      type: http
      scheme: bearer
      description: >-
        A Lath API key: lath_live_sk… or lath_test_sk… on a server,
        lath_live_pk… or lath_test_pk… in a browser.

````