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 LinkedIn, and what LinkedIn 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 LinkedIn 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 LinkedIn tools Codex gets
post_to_linkedin_page— publishes to a company Page — text, an image, a video, or a multi-image post — with alt text.post_to_linkedin— publishes to a personal profile, which stays switched off until you explicitly share that identity.list_linkedin_pages— the Pages you have shared with this brand, with their organization ids.schedule_post— queues it, carryinglinkedinOrganizationIdso the right identity posts.manage_linkedin_post— edit the copy of a post, or delete it.linkedin_page_analytics— organic Page performance — follower gains, Page views, and post impressions, clicks and engagement, per Page or per post.search_linkedin_ads— the LinkedIn Ad Library — the one public ad library that exposes real impression counts.
LinkedIn is the channel where identity is a permission rather than a preference. One person usually administers several companies’ Pages, so Hermoso makes the postable identities an explicit choice: only the Pages you have ticked under Manage accounts can be posted to, an unticked Page is refused server-side rather than in the UI alone, and the personal profile is off unless you turn it on. An agent that asks which Page rather than assuming is doing the right thing.
LinkedIn limits worth knowing before you automate anything
| Text | A LinkedIn post is capped at 3,000 characters. 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 only — “a LinkedIn post publishes to the profile or company Page — LinkedIn has no unlisted, private or draft post.” |
| Carousel | 2 to 20 images, from a company Page. Both bounds are LinkedIn’s own: “A MultiImage post is a post containing multiple images (minimum of 2 images and maximum of 20 images)”, and the schema adds “Only supports images”. Two refusals follow from that and both are by name rather than by silent downgrade: a video slide is refused because LinkedIn’s multi-image post cannot carry one, and a personal-profile carousel is refused with the way forward — “Pass linkedinOrganizationId (list_linkedin_pages) — a personal-profile carousel is not something Hermoso can publish.” |
| Which account | linkedinOrganizationId. Unset means the member’s own profile, never “probably the company” — so the field is how you say which Page, and leaving it out is a decision rather than an accident. |
Try it in Codex
Ask for it in ordinary language — these are sentences, not a DSL:
“Non-interactive: publish the weekly digest to the company Page with the four charts as a carousel and alt text on each, then print the post URL.”
That walks list_linkedin_pages → plan_ad → render_ad → post_to_linkedin_page → linkedin_page_analytics. 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 LinkedIn: the part that bites
Resolve list_linkedin_pages once and store the organization id in the job config. Leaving it unset does not mean “work it out” — it means the personal profile, which is off until explicitly shared, so an unattended run would fail on a permission rather than post to the wrong place. That fail-closed default is the right one; just do not rely on discovering it at 9am.
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 LinkedIn before you post
search_linkedin_ads reads the LinkedIn Ad Library, which is unusual among public ad libraries in exposing real impression counts — so B2B competitor research on LinkedIn can be ranked by actual delivery rather than by guesswork about what is running.
The paid half
create_linkedin_ads_campaign_group → create_linkedin_ads_campaign → create_linkedin_ads_creative builds the tree, and everything is born as a draft. set_linkedin_ads_status is the only switch that arms real money and it refuses without an explicit confirmation. One access note that is better said than discovered: LinkedIn meters ad writes by the API tier your own ad account holds — reporting and reads are unrestricted, and on the development tier an app may edit a small number of ad accounts, each registered by hand.
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: Facebook · Instagram · Threads · TikTok · YouTube · X · Pinterest — or see everything Codex can publish to.
Post to LinkedIn from: Claude · ChatGPT · Claude Code · Cursor · Cline · OpenClaw · Hermes · Ads from the command line
Frequently asked questions
Can Codex post to LinkedIn?
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 LinkedIn — and the ones that research the ads already running in your market and render the creative in the first place.
How do I connect LinkedIn 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 LinkedIn inside Hermoso under Settings → Connectors, which is an OAuth consent screen in a browser. After that Codex publishes to LinkedIn as an ordinary tool call.
Can Codex post privately or as a draft to LinkedIn?
No. LinkedIn has no unlisted, private or draft post — a post publishes to the profile or the company Page. Hermoso refuses a visibility LinkedIn cannot honour at the moment you ask for it, rather than quietly publishing something weaker.
Can Codex schedule a LinkedIn 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. LinkedIn is one of the eight channels that queue.
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