Deadsimple Email Templates API

openapi: 3.2.0
info:
  title: Dead Simple Email Templates API
  version: 0.1.0
  description: 'Email API for AI agents. Create inboxes, send and receive email,

    manage threads, and get real-time webhook notifications.


    ## Authentication

    All authenticated endpoints use Bearer token auth:

    ```

    Authorization: Bearer dse_your_api_key

    ```


    ## Agent self-signup

    Autonomous agents can provision an account, a key, and a live inbox in one

    unauthenticated call — no human, no verification email:

    ```

    POST /v1/auth/agent-signup

    ```

    That returns a `trial` account (1 inbox, 10 sends/hour, 25 sends/day) with a

    scoped key. `POST /v1/auth/claim` attaches a verified email and moves it to

    the Free plan, keeping the same key, inboxes and history.


    ## Sign in with Dead Simple (OpenID Connect)

    `https://id.deadsimple.email` is an OpenID Connect provider where the

    identity is an agent''s inbox: `sub` is the `inbox_id`, `email` is the inbox

    address. Discovery at `/.well-known/openid-configuration`, JWKS at

    `/.well-known/jwks.json`, ES256 id_tokens, authorization-code + PKCE S256,

    RFC 7591 registration at `/register`. Open clients (client_id = the app''s

    https origin) need no registration. An agent authenticates at `/authorize`

    with `Authorization: Bearer dse_...` plus `inbox_id=`, or with an ES256

    assertion signed by a key enrolled via `/v1/inboxes/{inbox_id}/identity/keys`;

    the one-call helper `POST /v1/inboxes/{inbox_id}/identity/sign-in` wraps

    this for SDKs and the MCP server. Endpoints on the `id.deadsimple.email`

    host are tagged **Identity Provider** below and carry their own `servers`

    entry.


    ## Pay per request (no API key)

    Twelve priced routes can be called with no credentials at all. They answer

    `402 Payment Required` carrying an x402 v2 `PAYMENT-REQUIRED` header (USDC

    on Base, Polygon or Solana, `exact` scheme, PayAI facilitator; the same

    JSON is repeated in the body for v1 clients) and, on `POST /v1/inboxes`,

    a `WWW-Authenticate: Payment` challenge for Stripe''s Machine Payments

    Protocol. Retry with `PAYMENT-SIGNATURE` (x402 v2), `X-PAYMENT` (v1) or

    `Authorization: Payment ` (MPP). x402 payments are verified

    before the work and settled after it; MPP charges first and refunds if

    the work fails. Prices: inbox $1.00, send/reply/reply-all/forward $0.01,

    reads $0.005. The paying wallet keys a `payg` account, and the first paid

    inbox returns `credentials` (an API key) in the response so later reads

    and sends within the plan are free. See the reusable `402` response and

    https://deadsimple.email/pay-per-request.html.


    ## Idempotency

    POST endpoints accept an `Idempotency-Key` header. Same key within 24h

    returns the cached response without re-executing.


    ## Rate Limits

    Every response includes rate limit headers:

    - `X-RateLimit-Limit` — requests per window

    - `X-RateLimit-Remaining` — remaining requests

    - `X-RateLimit-Reset` — window reset timestamp


    On `429`, a `Retry-After` header gives the seconds to wait. Per-account

    limits scale with plan (`rate_limit_rpm`); public/unauthenticated endpoints

    are additionally limited per IP.


    ## Webhook Reliability

    Every event is a durable delivery: the first attempt runs immediately and

    failures are retried on an exponential-backoff schedule (configurable per

    webhook via `/v1/webhooks/{id}/config`; default `[1, 30, 300, 1800, 7200,

    86400]` seconds). Deliveries are HMAC-SHA256 signed on **all plans**. The

    per-webhook delivery log (`/v1/webhooks/{id}/deliveries`) records every

    attempt with status and error, and any delivery can be replayed. Endpoints

    that fail repeatedly are auto-disabled.


    ## WebSocket Streaming

    Connect to `wss://ws.deadsimple.email?api_key=dse_...` for real-time events.


    After connecting, subscribe to specific inboxes/events:

    ```json

    {"action": "subscribe", "inbox_ids": ["..."], "events": ["message.received"]}

    ```


    Events are pushed as JSON with the same payload as webhooks. Send `{"action": "ping"}`

    to keep the connection alive (10-minute idle timeout).'
  contact:
    url: https://deadsimple.email
  license:
    name: MIT
servers:
- url: https://api.deadsimple.email
  description: Production
security:
- BearerAuth: []
tags:
- name: Templates
paths:
  /v1/templates:
    post:
      summary: Create an email template
      description: Reusable templates with {{variable}} substitution referenced by template_id on send.
      tags:
      - Templates
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - name
              properties:
                name:
                  type: string
                subject:
                  type: string
                text_body:
                  type: string
                html_body:
                  type: string
      responses:
        '201':
          description: Template created
      operationId: postV1Templates
      x-operation-id-source: derived
    get:
      summary: List templates
      tags:
      - Templates
      responses:
        '200':
          description: List of templates
      operationId: getV1Templates
      x-operation-id-source: derived
  /v1/templates/{template_id}:
    get:
      summary: Get a template
      tags:
      - Templates
      parameters:
      - name: template_id
        in: path
        required: true
        schema:
          type: string
      responses:
        '200':
          description: Template
      operationId: getV1TemplatesByTemplateId
      x-operation-id-source: derived
    put:
      summary: Update a template
      tags:
      - Templates
      parameters:
      - name: template_id
        in: path
        required: true
        schema:
          type: string
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
      responses:
        '200':
          description: Updated template
      operationId: putV1TemplatesByTemplateId
      x-operation-id-source: derived
    delete:
      summary: Delete a template
      tags:
      - Templates
      parameters:
      - name: template_id
        in: path
        required: true
        schema:
          type: string
      responses:
        '204':
          description: Template deleted
      operationId: deleteV1TemplatesByTemplateId
      x-operation-id-source: derived
components:
  securitySchemes:
    BearerAuth:
      type: http
      scheme: bearer
      description: API key (dse_...), session token (JWT), or OAuth 2.1 access token (dse_oat_..., obtained via the authorization-code + PKCE flow below)
    OAuth2:
      type: oauth2
      description: OAuth 2.1 for MCP clients. Public clients only (PKCE S256 required, no client secret). Supports RFC 7591 dynamic client registration at /oauth/register and discovery via /.well-known/oauth-authorization-server. Access tokens carry inbox/message permissions only (no billing, team, or API-key administration).
      flows:
        authorizationCode:
          authorizationUrl: https://api.deadsimple.email/oauth/authorize
          tokenUrl: https://api.deadsimple.email/oauth/token
          refreshUrl: https://api.deadsimple.email/oauth/token
          scopes:
            email: Send, receive, and manage email inboxes
    OpenIDConnect:
      type: openIdConnect
      openIdConnectUrl: https://id.deadsimple.email/.well-known/openid-configuration
      description: 'Sign in with Dead Simple. Relying parties use this to authenticate an agent by its inbox; it is not used to call the Dead Simple API itself. Scopes: openid, email, profile (open clients); owner_email, org, offline_access (registered clients only).'