Hermoso is a marketing MCP server: 301 tools over one OAuth’d endpoint that let an agent research the ads already running in a market, generate finished image and video ads, publish them, and build the paid campaigns behind them. Codex reaches all of it through one connection. This page is about one slice of that — what Codex can actually do on Facebook, and what Facebook will not let it do.
Connect Hermoso to Codex
- Create an API key. In Hermoso, open Settings → Agents & API keys and press ＋ Create API key. It looks like
hmk_…and carries real spend authority, so treat it like a password. - Add it to
~/.codex/config.toml. Codex reads TOML, not JSON — a copiedmcpServersblock will not load:[mcp_servers.hermoso] url = "https://app.hermoso.ai/mcp" http_headers = { "Authorization" = "Bearer <your key>" } - Ask Codex for something. “Pull my three closest competitors’ longest-running ads and remix the best hook into a 9:16 video,” or “post this render to the channel.” The agent picks the tools; you approve the spend.
The TOML detail is the one that trips people up: every other client in this list takes a JSON mcpServers object, and Codex takes [mcp_servers.<name>] with http_headers.
Then connect Facebook itself, once, under Settings → Connectors in Hermoso. That is an OAuth consent screen, so it is the one step that needs a browser — everything after it is a tool call.
The Facebook tools Codex gets
post_to_meta— publishes to the Page — text, an image, a video, or a multi-photo post — and takespageIdso it never has to guess which Page.schedule_post— queues the same post for a time you choose, on one calendar shared with every other channel.list_meta_pages— lists the Pages the account has connected, with their ids.manage_meta_post— edits the copy of a published post, or deletes it.list_meta_comments / reply_to_meta_comment / moderate_meta_comment— reads the comments under a post, replies as the Page, and hides or deletes what should not be there.meta_page_insights / meta_post_insights— Page-level and per-post reach, impressions and engagement.upload_meta_asset— puts a finished render into the ad account’s asset library.
Facebook is also the one channel with native remote scheduling — post_to_meta takes a scheduleAt between ten minutes and thirty days out and hands the timing to Meta itself. Instagram and Threads have no such thing in Meta’s API, and passing it for them is refused rather than quietly posted immediately.
Facebook limits worth knowing before you automate anything
| Text | A Facebook post can run to 63,206 characters, which is effectively no limit. It is enforced when the post is created or queued — refused while you are still there to fix it, rather than silently cut on the way out. |
|---|---|
| Visibility | Public or draft. A draft is a genuinely unpublished Page post, which is the useful one for review: it exists in Meta Business Suite and nobody outside can see it. There is no unlisted and no private — “a Facebook Page post is either published or held as an unpublished draft”. |
| Carousel | 2 slides and up, photos only. Meta publishes no maximum for attached_media that we could source, so Hermoso does not invent one and attribute it to Facebook — the only bound is ours, at 30 slides, and the refusal says whose it is: “Facebook publishes no documented maximum for attached_media, so this bound is ours, not theirs.” Video cannot ride in a Facebook photo carousel; that is a different edge on Meta’s API and Hermoso refuses rather than silently dropping the clip. |
| Which account | pageId. It matters the moment a brand connects more than one Page: the publish path refuses by name instead of picking one for you, and a schedule that could not carry the answer would turn that refusal into a failure hours later with nobody watching. |
Try it in Codex
Ask for it in ordinary language — these are sentences, not a DSL:
“Non-interactive: render a 1:1 image ad from the brand profile, post it to the Page as an unpublished draft, and print the post id as JSON.”
That walks find_competitors → search_meta_ads → plan_ad → render_ad → list_meta_pages → post_to_meta. Interactively Codex shows the call before it runs it. Non-interactively there is nobody to ask, which is worth designing around on any step that publishes or spends.
Codex on Facebook: the part that bites
Name the Page in the prompt or the config. With more than one connected Page the publish path refuses by name rather than picking one, which is correct — and in an unattended codex exec run there is nobody to ask, so the refusal becomes a failed job. Resolve it once with list_meta_pages and pin the id.
For unattended runs, prefer the hermoso CLI with --json over the full tool manifest — it is far cheaper in context and easier to assert on.
Research Facebook before you post
The Meta Ad Library is the richest public creative archive there is, and search_meta_ads reads it — by keyword or by page — covering both Facebook and Instagram placements. pull_competitor_ads and competitor_teardown build on it, and find_competitors works out who to point them at.
The paid half
Facebook is the deepest paid surface Hermoso has. create_meta_campaign, create_meta_adset and create_meta_ad build the whole tree with real targeting — geography down to a city radius, interests, behaviours, custom audiences and lookalikes, placements, dayparting, bid and cost caps. Everything is created PAUSED with no caller override, and the summary your agent reports is built from a read-back of what Meta actually stored, never from what was requested. Before a budget is committed, preview_meta_ad renders the real ad per placement as a link you can look at and estimate_meta_reach says how many people the targeting actually reaches. One warning that saves money: an ad set created with no locations defaults to the United States only, and the read-back says so loudly.
What Codex cannot do on its own
An agent with a budget is only useful if the blast radius is bounded, so the fence is in the server rather than in a prompt. Every ad campaign, ad set, ad group and ad is created paused, and the status switches that arm real money refuse to run without an explicit confirmation flag. Every render is quoted first — hermoso_capabilities publishes each model’s exact credit cost before anything spends — and credits are reserved before the first provider call and settled at the exact cost afterwards, so a failed dispatch refunds rather than leaving you billed for nothing. Deletes are confirm-gated too, and every campaign tree is read back from the ad platform before your agent tells you what it built.
One step is deliberately not headless: linking an account is an OAuth consent screen, so you connect the channel once in a browser. Everything after that is a tool call.
The rest of the matrix
From Codex, post to: Instagram · Threads · TikTok · YouTube · X · LinkedIn · Pinterest — or see everything Codex can publish to.
Post to Facebook from: Claude · ChatGPT · Claude Code · Cursor · Cline · OpenClaw · Hermes · Ads from the command line
Frequently asked questions
Can Codex post to Facebook?
Yes, through Hermoso's MCP server. Create an API key in Hermoso under Settings → Agents & API keys, then add https://app.hermoso.ai/mcp to Codex with an Authorization: Bearer header. Codex then has 301 tools, including the ones that publish to Facebook — and the ones that research the ads already running in your market and render the creative in the first place.
How do I connect Facebook to Codex?
Two steps, once each. Create an API key in Hermoso under Settings → Agents & API keys, then add https://app.hermoso.ai/mcp to Codex with an Authorization: Bearer header. Then connect Facebook inside Hermoso under Settings → Connectors, which is an OAuth consent screen in a browser. After that Codex publishes to Facebook as an ordinary tool call.
What is the Facebook caption limit when posting from Codex?
A Facebook post can run to 63,206 characters, which is effectively no limit. Hermoso enforces it when the post is created or queued, so Codex is told immediately rather than failing later when nobody is watching.
Can Codex schedule a Facebook post for later?
Yes. schedule_post queues it on one calendar shared with every other channel, with a per-channel caption if the copy should differ, and list_scheduled and cancel_scheduled read and pull it back. Facebook is one of the eight channels that queue.
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