---
title: "Send a LinkedIn reply on an existing conversation (single call, idempotent)"
method: POST
path: "/api/v1/replies"
tags: ["Replies"]
---

# Send a LinkedIn reply on an existing conversation (single call, idempotent)

`POST /api/v1/replies`

## Request

- Base URL: `https://app.reachium.io`
- URL: `https://app.reachium.io/api/v1/replies`
- Auth: HTTP bearer

The single-call REST path for sending an approved reply. Unlike POST /api/v1/actions/sendReply (the MCP bridge), this endpoint sends immediately, with no separate preview/confirm step. Shares the SAME per-account daily reply cap as the MCP sendReply tool.

## Headers

- `Idempotency-Key` string, required

## Request body

- object
  - `chat_id` string, required
  - `text` string, required

## Response `201`

Sent.

- object
  - `data` object, required
    - `chat_id` string, required
    - `sent_at` string, date-time, required
  - `error` unknown, required

## Other responses

- `400`: Invalid body (code invalid_request: missing/blank chat_id or text, or text over 4000 chars) or a missing/malformed Idempotency-Key header (codes idempotency_key_required or invalid_idempotency_key).
- `401`: Missing or invalid API key. Send `Authorization: Bearer rmcp_...` (code unauthorized).
- `402`: Workspace billing is blocked; mutating requests are refused (code billing_blocked).
- `403`: The key's granted scopes do not satisfy this endpoint's minimum required scope (code insufficient_scope).
- `404`: chat_id does not belong to this workspace (code not_found).
- `409`: This Idempotency-Key has an unresolved in-flight or ambiguous outcome (code request_in_flight). It is not automatically taken over; reconcile before choosing a new key.
- `422`: This Idempotency-Key was already used with a DIFFERENT chat_id/text (code idempotency_key_reuse).
- `429`: Either the shared rate-limit bucket (code rate_limited) or this LinkedIn account's daily reply cap (code daily_reply_cap_reached).
- `500`: Unhandled server error (code internal_error).
- `502`: The LinkedIn send itself failed (code send_failed).
- `503`: Either the daily-cap check errored transiently (code cap_check_failed) or the billing check failed (code billing_check_failed); both safe to retry.

---

[API](https://skmtc.dev/reachium/apis/reachium-api.md) · [All operations](https://skmtc.dev/reachium/apis/reachium-api/llms.txt) · [OpenAPI document](https://skmtc.dev/reachium/apis/reachium-api/revisions/11682826692b?raw)