Social media inbox: one place for DMs and comments, and the API version
A social media inbox pulls DMs and comments from several accounts into one list you answer from. What it can show depends entirely on each platform's API: Instagram, Facebook Messenger, WhatsApp and Telegram expose messages, X charges per call for them, LinkedIn does not expose them at all. Prices and limits below were checked on October 20, 2026.
What a social inbox actually is
Two different objects get sold under the same name, and the difference decides whether a tool is useful to you.
A message inbox reads direct messages: a thread per contact, an unread flag, a reply box. A comment queue reads public comments on your own posts: one row per comment, a reply that appears in the feed, a hide or delete action. Most vendors put both behind one tab and call it a unified social inbox. The APIs behind them are completely separate, which is why a tool can be excellent at one and absent on the other.
PlugKit splits them on purpose. Conversations and messages live under /v1/inbox/conversations, documented in the messaging guide. Comments and mentions live under /v1/engagement, documented in the engagement guide. Same account list, two queues, because no platform ships them together.
All social media messages in one place: what each API gives you
This is the table nobody publishes, because it makes the category look smaller than the marketing does.
| Platform | DMs readable by an API | Comments readable by an API | The catch |
|---|---|---|---|
| Yes | Yes, on your own media | Free-form replies only within 24 hours of the contact's last message | |
| Facebook Messenger and Page | Yes | Yes, on your own Page posts | Same 24-hour window on messages |
| Yes | No comments exist on WhatsApp | Past 24 hours, only an approved template goes out | |
| Telegram | Yes | No comments exist for a bot account | No time window, but the contact must message your bot first |
| Threads | No DM API | Yes, plus mentions | You cannot delete a comment, only hide it |
| X | Paid, elevated access | Replies are posts, not comments | Billed per call: $0.010 to read a DM, $0.015 to send one |
| Restricted to approved partners | Needs Community Management review | No self-serve route to member messages |
The 24-hour rule is the one that catches everyone. On Instagram and Facebook Messenger, an unanswered DM from Tuesday cannot be answered freely on Thursday. The documented exception is a private reply to a comment, allowed once per comment within 7 days, which is exactly the mechanism behind comment-to-DM automation.
LinkedIn is the honest hole in every unified inbox on the market. Its Messages API opens with "Usage of this API is restricted to approved partners, subject to limitations via API agreement", and even approved partners must tie each message to a specific member action, because "Member actions do not include an automated or scheduled event". Any product promising LinkedIn DMs in a shared inbox is driving a browser session, not calling an API. The full picture is in LinkedIn automation tools.
What a unified social inbox cannot show you
Four gaps, all structural rather than fixable by a better vendor.
Instagram story replies are not comments. A story has no comment object. When someone replies to your story, it arrives as a direct message, so it lands in the message inbox and counts against the same 24-hour window. Expecting it in a comment queue is a category error.
Comment coverage stops well short of the account list. A tool can publish to eight platforms and still read comments on three. PlugKit is explicit about it: comments work on Instagram, Facebook Page and Threads, and mentions only on Threads.
Hidden state is often unknown. The engagement docs warn that a null hidden flag means the platform does not report it for that object, and add: "Do not read null as visible." A dashboard that paints every unknown as visible is guessing.
Nothing is retroactive. Inboxes are built on webhooks plus an on-demand sync. Connect an account today and you get what arrives from today, not three years of history.
Social inbox tools and what they cost
Prices below were read on each vendor's own pricing page on October 20, 2026. Per-seat and per-channel billing are not comparable at face value, so the third column is what you actually pay to put one person in front of five accounts.
| Tool | List price | Five accounts, one person | DMs | Comments |
|---|---|---|---|---|
| Buffer | $5 per channel per month (Essentials), $10 (Team) | $25 | Not mentioned on the pricing page | Yes, on every level |
| Zernio | 2 accounts at no cost, then $6 per account per month to 10 | $18 | Yes | Yes |
| Metricool | From $25 per month monthly billing (Starter, 5 brands) | $25 | Yes, X needs an add-on | Yes |
| Hootsuite | From $99 per month (Standard, 10 accounts) | $99 | Yes | Yes |
| Sprout Social | $99 per seat per month billed monthly (Essentials, 5 profiles) | $99 | Yes | Yes |
| PlugKit | $49 a month for 5 connected accounts | $49 | Yes | Yes |
Read that honestly. If a shared inbox with assignment, saved replies and a review workflow is the job, Sprout Social and Hootsuite are built for it and PlugKit is not. If the job is cheap coverage of a handful of accounts, Zernio undercuts everyone and Buffer is close. Sprout Social and Hootsuite bill per seat, so the column above triples the moment a second person joins.
Two notes on the numbers. Metricool's annual prices are lower, from $20 per month for 5 brands, and its X inbox is an add-on rather than a default. Zernio meters outbound messages past the first ten thousand each month, so a broadcast-heavy account pays more than the table suggests. Both figures come from their own pricing pages today.
PlugKit's case is narrow and worth stating plainly: $49 a month for 5 connected accounts, cancel anytime, with the inbox reachable by an API and by an agent rather than only by a human in a browser. Seven days free, no card, one connected account during the trial.
The API version: building your own inbox
If you want the queue inside your own product, the shape is the same everywhere.
- Connect accounts and hold the tokens. The hard part, and the reason hosted layers exist. See social media access tokens for why they expire quietly.
- Subscribe to webhooks. Inbound messages arrive as
message.received; new comments arrive on the platform's comments subscription. Meta's own advice in the Instagram Platform docs is blunt: "We strongly recommend using webhooks to prevent rate limiting." - Sync on demand for the gaps. A webhook you missed while your server was down is gone.
POST /v1/inbox/conversations/syncandPOST /v1/engagement/syncexist for exactly that. - Respect the windows in code, not in the UI. Check the last inbound timestamp before offering a free-form reply box, or your send fails at the platform.
- Mind the rate limits. Instagram's Conversations API allows 2 calls per second per professional account; the Send API allows 100 per second for text. Those are per account, not per app.
The MCP route skips steps 1 to 3 entirely: a hosted server exposes the inbox as tools, and the agent reads and answers. That setup is walked through in the Hermes Agent guide, and the choice between handing an agent an MCP server or a plain REST API is argued in MCP or REST API for your agent.
FAQ
What is a social media inbox?
It is one list that collects direct messages, and usually comments, from several connected accounts so you answer them in one place. The coverage is set by each platform's API rather than by the tool, which is why no inbox on the market covers every network equally.
Can I see all my social media messages in one place?
For Instagram, Facebook Messenger, WhatsApp and Telegram, yes, through the official messaging APIs. X direct messages need paid elevated access and are billed per call. LinkedIn member messages are restricted to approved partners, so no self-serve tool reads them compliantly.
Why can't I reply to an old Instagram DM from my inbox tool?
Meta only accepts free-form messages within 24 hours of the contact's last message. After that the thread is closed to normal replies. The documented exception is a private reply to a comment, allowed once per comment within 7 days, and on WhatsApp an approved template.
Do unified inboxes show Instagram story replies?
They show them as direct messages, because a story has no comment object on Instagram. A reply to your story is a DM, subject to the same 24-hour window, so look for it in the message list and not in the comment queue.
What is the cheapest social inbox for five accounts?
On the prices read on October 20, 2026, Zernio at $18 a month and Buffer at $25 are the cheapest for one person on five accounts. Hootsuite and Sprout Social both start near $99 and bill per seat. Pick on workflow rather than price if several people answer messages.
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