set_youtube_thumbnail

SERVERHermoso SOURCEhttps://app.hermoso.ai/mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade D, identity unverified Pull the record →

This record as markdown: /tools/hermoso/set-youtube-thumbnail.md

WHAT IT DOES

What set_youtube_thumbnail does on Hermoso

AI agents use set_youtube_thumbnail to create or update resources in Hermoso, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Hermoso environment.

RISK

Why set_youtube_thumbnail is rated Medium

An AI agent can call set_youtube_thumbnail faster than any human can review: one bad instruction and it creates or modifies resources in Hermoso by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs set_youtube_thumbnail safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Hermoso, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For set_youtube_thumbnail, this is the rule to start with:

set_youtube_thumbnail Rate-limited

set_youtube_thumbnail stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_youtube_thumbnail": {
      "limits": [
        {
          "counter": "set_youtube_thumbnail_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Hermoso, apply this rule, and every set_youtube_thumbnail call is checked against it from then on.

FAQ

Questions about set_youtube_thumbnail

What does the set_youtube_thumbnail tool do? +

Set the CUSTOM THUMBNAIL on a video already on the connected channel, using a Hermoso image — a make_thumbnail render, a generated image, or a frame. The thumbnail is the single biggest lever on YouTube click-through and YouTube otherwise auto-picks a frame, so a published video without one is leaving reach on the table. It changes ONLY the thumbnail — video, title and privacy are untouched — but it is public and immediate, so show the user which image is going on which video and get a yes first. Custom thumbnails require a VERIFIED YouTube channel (a phone number at youtube.com/verify); without it YouTube refuses and the error says so. Images over YouTube’s 2MB cap are compressed automatically. The image must be Hermoso-HOSTED, which is not the same as Hermoso-GENERATED: the user’s own artwork works, put it through upload_file first and pass the URL that returns. An arbitrary external host is refused. 0 credits. Needs a connected YouTube channel. It is categorised as a Write tool in the Hermoso MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_youtube_thumbnail? +

Register the Hermoso MCP server in PolicyLayer and add a rule for set_youtube_thumbnail: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Hermoso. Nothing to install.

What risk level is set_youtube_thumbnail? +

set_youtube_thumbnail is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_youtube_thumbnail? +

Yes. Add a rate_limit block to the set_youtube_thumbnail rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block set_youtube_thumbnail completely? +

Set action: deny in the PolicyLayer policy for set_youtube_thumbnail. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides set_youtube_thumbnail? +

set_youtube_thumbnail is provided by the Hermoso MCP server (https://app.hermoso.ai/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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