Hermoso is a marketing MCP server: 850+ 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. Le Chat reaches all of it through one connection. This page is about one slice of that — what Le Chat can actually do on YouTube, and what YouTube will not let it do.
Connect Hermoso to Le Chat
- Copy the connector URL.
https://app.hermoso.ai/mcp - Le Chat → Intelligence → Connectors → + Add Connector → Custom MCP Connector. Name it Hermoso and paste the URL.
- Press Connect and approve. Le Chat detects Hermoso’s OAuth sign-in with dynamic client registration and opens the consent page. Sign in with your Hermoso account; there is no key to paste.
- Ask Le Chat 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.
Adding a custom connector is an admin action in Le Chat. On the Free, Pro and Student plans the account owner is the admin, so you can add Hermoso yourself, free plan included; on a team plan an admin adds it. The steps are quoted from Mistral’s MCP connector documentation, read on 2026-09-23. Hermoso is not affiliated with or endorsed by Mistral AI.
Then connect YouTube 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 YouTube tools Le Chat gets
post_to_youtube— uploads a finished video with a title, a description of up to 5,000 characters, up to 30 tags, and a privacy setting.schedule_post— queues the upload — with the description and tags carried through, which is not something to take for granted.set_youtube_thumbnail— puts a designed thumbnail on the upload. It is the single biggest lever on click-through, and YouTube otherwise picks a frame more or less at random.make_thumbnail— generates that thumbnail in the first place.update_youtube_video / list_youtube_videos— edit an upload’s metadata, or list your own uploads — including unlisted and private ones a public search cannot see.youtube_video_insights / youtube_channel— views, watch time, average view percentage and subscribers gained.list_youtube_comments / reply_to_youtube_comment— read and answer comments as the channel.
The unit really is a video: post_to_youtube takes a videoUrl and there is no image path at all. Two smaller gates worth knowing before an automated upload: a Google project that has not been verified has videos.insert locked to private regardless of what you ask for, and custom thumbnails need a phone-verified channel.
YouTube limits worth knowing before you automate anything
| Text | A YouTube title is capped at 100 characters — and a scheduled item’s text becomes the title. The description is a separate field of up to 5,000 characters, carrying up to 30 tags. 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, unlisted or private. There is no Studio draft — “YouTube’s API can upload as public, unlisted or private, but it cannot create a Studio draft”, so unlisted is the closest thing to a review state, and it is what an immediate post defaults to so an ad-ready upload is not accidentally public. |
| Carousel | Refused, by name. “YouTube’s unit is a video, not a set of stills. Turn the slides into a video (Hermoso can stitch them) and post that instead, or drop YouTube from this post.” That is not a limitation Hermoso invented to avoid work — it is what YouTube is — and the refusal comes at enqueue, with the way forward attached, rather than as a silently posted first slide. |
| Which account | None — YouTube publishes to the connected channel. |
Try it in Le Chat
Ask for it in ordinary language — these are sentences, not a DSL:
“Upload this film unlisted with a title under 100 characters, a full description with our link, ten tags and a generated thumbnail, then send me the link.”
That walks make_thumbnail → post_to_youtube → set_youtube_thumbnail → youtube_video_insights. Le Chat lets you set each connector function to Always allow or leave it asking. Mistral’s own advice is to pre-authorise read functions and keep write functions on manual approval, and that is the right split here: research and list tools can run freely, anything that publishes, schedules or deletes should ask.
Le Chat on YouTube: the part that bites
Unlisted is the only review state YouTube’s API has, so it is the right default, and making it public later is update_youtube_video. Ask for the description explicitly: otherwise the text you give becomes the 100-character title, and the links belong in the description’s 5,000 characters.
Le Chat’s custom connectors do not pick up new tools after you connect; the list is what it loaded at that moment. Hermoso starts a connector on a short list and includes find_tools and call_tool, which reach every other tool by name, so a tool missing from the loaded list is still one request away.
Research YouTube before you post
search_youtube searches the public YouTube index — which is a different question from “what have I uploaded”, and list_youtube_videos is the tool for that one. For a competitor’s film, analyze_video returns the voiceover, the on-screen text and the beat list with timestamps, which is what you actually want before rebuilding a hook.
The paid half
Hermoso’s Google Ads tools build search, display and Performance Max campaigns — the whole tree in one atomic operation, read back from Google before your agent narrates it — plus Keyword Planner volumes, conversion actions, and sitelinks and callouts created and attached. There is no YouTube video-campaign builder, and it would be wrong to imply one; a YouTube video asset can be uploaded and attached, but the campaign types Hermoso creates are search, display and Performance Max.
What Le Chat 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 Le Chat, post to: Facebook · Instagram · Threads · TikTok · X · LinkedIn · Pinterest · Bluesky · Telegram — or see everything Le Chat can publish to.
Post to YouTube from: Claude · ChatGPT · Claude Code · Cursor · Codex · Cline · OpenClaw · Grok Bot · Hermes · Gemini CLI · Perplexity
Frequently asked questions
Can Le Chat post to YouTube?
Yes, through Hermoso's MCP server. In Le Chat, add https://app.hermoso.ai/mcp as a custom connector and approve it with your Hermoso account — there is no key to paste. Le Chat then has 850+ tools, including the ones that publish to YouTube — and the ones that research the ads already running in your market and render the creative in the first place.
How do I connect YouTube to Le Chat?
Two steps, once each. In Le Chat, add https://app.hermoso.ai/mcp as a custom connector and approve it with your Hermoso account — there is no key to paste. Then connect YouTube inside Hermoso under Settings → Connectors, which is an OAuth consent screen in a browser. After that Le Chat publishes to YouTube as an ordinary tool call.
Does Le Chat need my YouTube password?
No. You connect YouTube to Hermoso once through an OAuth consent screen in a browser, and Le Chat then reaches it as a tool call. Linking an account is the one step that is not headless; nothing after it needs a password, and no credential is ever handed to the model.
Can Le Chat research YouTube before it posts?
Yes. search_youtube searches the public YouTube index, list_youtube_videos reads your own uploads including unlisted ones, and analyze_video returns a competitor film’s voiceover, on-screen text and beat list with timestamps.
Start free — 30 credits at signup and 250+ more to earn, and every feature on every plan. Credits are spent only on AI models and Ad Spy research; posting, scheduling, ads management and analytics are free.
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