> ## 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.

# email.sender.set

> Changes the project's sending identity on the shared parent: the local part before the @, the subdomain label, and the display name. Every field is optional; omitted fields are left alone. Changing the label changes the address every future message comes from, and frees the old one for reuse by another project, so it is a live change rather than an alias.



## OpenAPI

````yaml /api-reference/openapi.json post /email/sender/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:
  /email/sender/set:
    post:
      tags:
        - email
      summary: email.sender.set
      description: >-
        Changes the project's sending identity on the shared parent: the local
        part before the @, the subdomain label, and the display name. Every
        field is optional; omitted fields are left alone. Changing the label
        changes the address every future message comes from, and frees the old
        one for reuse by another project, so it is a live change rather than an
        alias.
      operationId: email.sender.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:
                local:
                  description: >-
                    The part before the @, like "hello" or "team". Letters,
                    digits, dot, hyphen and underscore.
                  type: string
                  minLength: 1
                  maxLength: 64
                label:
                  description: >-
                    The subdomain label under the sending parent. Must be unused
                    by any other project.
                  type: string
                  minLength: 1
                  maxLength: 63
                name:
                  description: >-
                    The display name beside the address. Pass null to follow the
                    project name.
                  anyOf:
                    - type: string
                      minLength: 1
                      maxLength: 100
                    - type: 'null'
              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:
                      address:
                        type: string
                      local:
                        type: string
                      domain:
                        type: string
                      label:
                        type: string
                      parent:
                        type: string
                      name:
                        type: string
                      nameIsDefault:
                        type: boolean
                    required:
                      - address
                      - local
                      - domain
                      - label
                      - parent
                      - name
                      - nameIsDefault
                    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.

````