Deadsimple Email Messages API

openapi: 3.2.0
info:
  title: Dead Simple Email Messages 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:


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# Full source: https://artifacts.apis.io/deadsimple-email/openapi/deadsimple-email-messages-api-openapi.yml