API reference · Capumattu

Base URL: https://mailroom.capumattu.com. All /v1 routes need Authorization: Bearer <api_key>. The dashboard calls the same routes with its session instead; see Dashboard and account API.

#Conventions

Lists use cursor pagination: ?cursor=&limit= (max 100). Responses are { data, next_cursor }.
Errors are always { "error": { "code", "message" } }.
Send and reply honour an Idempotency-Key header, so retries never send twice.
Times are ISO 8601 in UTC.

#Inboxes

Method & path	Notes
`POST /v1/inboxes`	`{ username?, display_name?, client_id?, metadata?, domain? }`. Random readable username if omitted. Idempotent on `client_id` (200 with the existing inbox). `domain` is one of your verified domains (default `agents.capumattu.com`). Send `{ ttl_seconds }` (60–86 400) instead for a temporary inbox; `username`, `domain` and `client_id` are not allowed with it.
`GET /v1/inboxes`	List inboxes. Filter on your own fields with `?metadata.<key>=<value>` (exact string match). Temporary inboxes are left out unless you pass `?include_temporary=true`; `?temporary=true` lists only them.
`GET /v1/inboxes/:id`	One inbox, with its `metadata`. Every inbox has `temporary` (boolean) and `expires_at` (ISO time, or null).
`PATCH /v1/inboxes/:id`	`{ display_name?, metadata?, ttl_seconds? }`. Metadata is merged; a `null` value deletes the key. See Metadata. `ttl_seconds` extends a temporary inbox, counted from now, up to 24 hours after it was created.
`DELETE /v1/inboxes/:id`	Soft delete. The address is never reused. On a temporary inbox this wipes its messages, attachments and threads right away.

#Messages

Method & path	Notes
`POST /v1/inboxes/:id/messages/send`	`{ to, cc?, bcc?, subject, text?, html?, attachments?: [{ filename, content_type, content_base64 }], labels? }`. Returns 202 with `status: "queued"`.
`POST /v1/inboxes/:id/messages/:messageId/reply`	`{ text?, html?, attachments?, reply_all? }`. Sets `In-Reply-To` and `References`, adds `Re:`, stays in the thread.
`GET /v1/inboxes/:id/messages`	Filters: `labels=a,b` (must have all), `is_read`, `direction`.
`GET /v1/inboxes/:id/messages/wait`	Long-poll. `timeout` (1–60 s, default 30), `since` (ISO, default now), `from`, `subject`, `direction` (default inbound). Returns `{ data: Message \| null }`: the oldest message after `since`, or null on timeout.
`GET /v1/inboxes/:id/verification`	Long-poll for a login code or magic link. `timeout`, `since`, `from`. Returns the newest matching message’s code, link and confidence, or null.
`GET /v1/messages/:id`	One message.
`PATCH /v1/messages/:id`	`{ add_labels?, remove_labels?, is_read? }`.
`GET /v1/messages/:id/raw`	Original MIME (`message/rfc822`, download only).
`POST /v1/messages/:id/draft-reply`	`{ instructions? }` (up to 2,000 characters). Returns `{ text, citations: [{ knowledge_id, title }], model }`. Never sends. Needs AI processing `full`; see Reply drafts.
`GET /v1/attachments/:id`	Streams the file (download only, `nosniff`, sandbox CSP).

#Threads and search

Method & path	Notes
`GET /v1/inboxes/:id/threads`	Threads in an inbox, newest first.
`GET /v1/threads/:id`	The thread plus its messages in order. Threads carry `labels` and `metadata`.
`PATCH /v1/threads/:id`	`{ metadata?, add_labels?, remove_labels? }`. Metadata is merged; `null` deletes a key.
`GET /v1/search?q=&inbox_id=`	Postgres full-text search with web-search syntax (`"exact phrase"`, `-exclude`, `or`), ranked, with a `snippet`.

#Contacts

Method & path	Notes
`GET /v1/contacts`	`?q=&label=&cursor=&limit=`. Newest `last_seen_at` first. `q` matches address or name. `?metadata.<key>=<value>` filters.
`GET /v1/contacts/:id`	The contact plus `recent_threads` (up to 10, across all inboxes).
`GET /v1/contacts/by-address/:address`	Look a contact up by email address. 404 if you have never exchanged mail with it.
`PATCH /v1/contacts/:id`	`{ name?, notes?, metadata?, add_labels?, remove_labels? }`. Notes up to 10,000 characters. See Contacts and memory.

#Knowledge

Method & path	Notes
`GET /v1/knowledge`	`?inbox_id=&cursor=&limit=`. Items have an `excerpt` (up to 200 characters) instead of the `body`.
`POST /v1/knowledge`	`{ title, body, inbox_id? }`. Body up to 200,000 characters of plain text or markdown. No `inbox_id` means all inboxes. 201 with the document.
`GET /v1/knowledge/:id`	One document, with its body.
`PATCH /v1/knowledge/:id`	`{ title?, body?, inbox_id? }`.
`DELETE /v1/knowledge/:id`	Deletes the document.
`GET /v1/knowledge/search`	`?q=&inbox_id=&limit=`. Ranked full-text search. With `inbox_id`, workspace-wide documents are included. Returns `{ data: [{ id, title, inbox_id, rank, snippet }] }`.

#Webhooks

Method & path	Notes
`POST /v1/webhooks`	`{ url, events?, inbox_ids?, enabled?, secret? }`. The secret is returned only here.
`GET /v1/webhooks` · `GET /v1/webhooks/:id`	Returns `secret_hint`, never the secret.
`PATCH /v1/webhooks/:id` · `DELETE /v1/webhooks/:id`	Change events, scope or `enabled`; delete.
`POST /v1/webhooks/:id/test`	Sends a `webhook.test` event.
`GET /v1/webhooks/:id/deliveries`	Recent attempts: status, attempts, last status code and error, next retry.

#Domains

Method & path	Notes
`POST /v1/domains`	`{ domain, receiving? }` → 201 with `status: "pending"` and the DNS `records` to publish. How many depends on the plan (Free 1, Builder 10, Team 50; `403 plan_limit_domains` past it). See Custom domains.
`GET /v1/domains`	List your domains.
`GET /v1/domains/:id`	One domain with its `records` and each record’s last check result.
`POST /v1/domains/:id/verify`	Checks the DNS records now and returns the domain. At most once every 10 seconds per domain.
`PATCH /v1/domains/:id`	`{ receiving }` turns receiving on or off.
`DELETE /v1/domains/:id`	`409 domain_in_use` while inboxes use the domain. `?force=true` deletes those inboxes too.

#The message object

Every message has text, html, extracted_text, headers, labels, status (queued | sent | delivered | bounced | complained | failed | received), attachment metadata, contact_id (inbound: the sender’s contact; outbound: the first recipient’s; or null), and ai.verification ({ code, link, confidence, jev_probability } or null). Inbound messages also get the JEV fields described below once they have been categorised.

Labels you may see on inbound mail: spf-fail and dmarc-fail (authentication failed), the ai:* labels below, and bounce-report on delivery-failure notices.

#Categories and risk flags

Shortly after an inbound message is stored, JEV reads the sender, subject, the first 3,000 characters of the text, our own SPF/DKIM/DMARC results and the attachment names, and answers six questions in one call. The results are merged into message.ai and a message.enriched webhook fires. message.received is never delayed by this. Bounce reports are not categorised.

message.ai

{
  "verification": null,
  "category": { "label": "billing", "confidence": 0.94, "probabilities": { "billing": 0.94, "other": 0.06 } },
  "risk": { "injection": 0.01, "phishing": 0.03 },
  "needs_human": 0.22,
  "urgency": { "level": "normal", "score": 1.4, "confidence": 0.72 },
  "auto_reply": 0.03,
  "model": "jev",
  "enriched_at": "2026-09-25T12:00:04.000Z"
}

Field	Meaning
`category`	One of `support`, `sales`, `billing`, `verification`, `notification`, `newsletter`, `personal`, `other`, with its confidence and the probability of each option.
`risk.injection`	Probability that the message tries to instruct an AI (ignore its rules, reveal data, act for the sender).
`risk.phishing`	Probability of credential harvesting, a scam or impersonation. The authentication results are part of the input.
`needs_human`	Probability that a person should handle it: legal matters, complaints, threats, sensitive personal data.
`urgency`	`level` is the most likely of `low`, `normal`, `high`, `critical`; `score` is the expected value from 0 to 3.
`auto_reply`	Probability of an out-of-office, auto-responder, ticket acknowledgement or bulk mail.
`enrichment_error`	Set instead of the fields above when enrichment gave up after its retries. The message is otherwise unaffected.

All probabilities are 0 to 1. A label is only added when a score passes its threshold, so a message without ai:phishing can still have a non-zero risk.phishing. Read the scores if you need a different cut-off.

Label	Added when
`ai:<category>`, e.g. `ai:billing`	Category confidence is 0.6 or more.
`ai:uncertain`	Category confidence is under 0.6 (instead of a category label).
`ai:injection-risk`	`risk.injection` is 0.8 or more.
`ai:phishing`	`risk.phishing` is 0.8 or more.
`ai:needs-human`	`needs_human` is 0.7 or more.
`ai:auto-reply`	`auto_reply` is 0.8 or more.
`ai:urgent`	`urgency.level` is `high` or `critical`.

Labels are only ever added; your own labels are never removed or reordered. Filter on them with GET /v1/inboxes/:id/messages?labels=ai:billing,ai:urgent (a message must have every label you list).

#Limits and errors

Status & code	When
`401 unauthorized`	Missing or revoked API key.
`403 forbidden`	The action needs a workspace owner, for example changing AI processing.
`403 ai_disabled`	A reply draft was requested but AI processing is not `full`.
`403 org_suspended`	Sending is paused for the workspace (bounce rate over 5% or complaint rate over 0.1% in the last 7 days). Clean the recipient list, then write to abuse@capumattu.com.
`403 temporary_inbox_receive_only`	Send or reply from a temporary inbox. They only receive.
`403 domain_not_verified`	Send from an inbox whose domain failed its DNS checks. Fix the records and check the domain again.
`409 domain_taken` · `409 domain_in_use`	The domain is verified by another workspace; or you tried to delete a domain that inboxes still use.
`413`	Message or attachment over the size limit.
`422 recipient_suppressed`	The address hard-bounced or complained before.
`402 plan_limit_emails`	The plan’s monthly emails are used up. Receiving keeps working. See Plans and limits for every plan error.
`403 plan_limit_inboxes`	The plan’s inboxes are all in use.
`429 daily_send_limit_exceeded`	This inbox’s daily send limit reached. Resets at 00:00 UTC.
`429 org_daily_limit_exceeded`	The workspace’s daily send cap (from its plan) reached. Resets at 00:00 UTC.
`429 rate_limited`	Too many requests for this API key in a minute.
`429 temporary_inbox_limit`	25 temporary inboxes are already active in the workspace. Creating them is also limited to 60 an hour.
`503 llm_unavailable`	The drafting model didn’t answer. Nothing was sent; try again later.

#Dashboard and account API

The dashboard at capumattu.com uses these routes with a session cookie (cm_session) instead of an API key. Requests that change data (POST, PATCH, DELETE) must send X-Requested-With: capumattu-web, or they get 403 csrf. You don’t need them to build an agent; they are listed so nothing the dashboard does is hidden.

Method & path	Notes
`POST /platform/auth/magic-link`	`{ email }`. Always `204`. Emails a sign-in link from login@capumattu.com, valid 15 minutes, usable once. Rate-limited per address and per IP.
`POST /platform/auth/verify`	`{ token }` from the link. `200 { user, org }` and sets the session cookie; `400 invalid_token` if the link expired or was used.
`GET /platform/auth/github`	Starts GitHub sign-in (`?next=/app`). Not enabled at launch.
`POST /platform/auth/logout`	`204`. Ends the session.
`GET /platform/me`	`{ user, org }`, or `401 unauthorized`. The org includes `status`, `daily_send_limit` and `ai_processing`.
`GET /platform/api-keys`	API keys: name, prefix, created, last used, revoked. Never the secret.
`POST /platform/api-keys`	`{ name }`. `201 { api_key, key }`: the full key is shown this once.
`DELETE /platform/api-keys/:id`	Revokes the key. `204`.
`GET /platform/usage`	`?days=30` (up to 90). Sends and receives today, the limits, the inbox count and a daily series.
`PATCH /platform/org`	`{ name?, ai_processing? }`. Owners only (`403 forbidden` otherwise). `ai_processing` is `off`, `categorize` or `full`.