Upload media files to microCMS using JS SDK (Management API). Supports two methods: 1) Upload file data (base64) with filename and mimeType, 2) Upload from external URL. Returns microCMS asset URL. Requires media upload permissions. Available on Team, Business, Advanced, and Enterprise plans.
AI agents use microcms_upload_media to create or update resources in microCMS MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your microCMS MCP Server environment.
This tool creates and stores new media assets in microCMS, which is a reversible write operation. While uploads add content to the system, they do not permanently destroy data or execute arbitrary code.
From the tool's definition Tool description explicitly states 'Upload media files to microCMS' and 'Returns microCMS asset URL', indicating it creates new media assets in the system.
Documented attack patterns abuse exactly the kind of access microcms_upload_media gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and microCMS MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for microcms_upload_media:
{
"version": "1",
"default": "deny",
"tools": {
"microcms_upload_media": {
"limits": [
{
"counter": "microcms_upload_media_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}microcms_upload_media 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.
Free to start. No card required.
Upload media files to microCMS using JS SDK (Management API). Supports two methods: 1) Upload file data (base64) with filename and mimeType, 2) Upload from external URL. Returns microCMS asset URL. Requires media upload permissions. Available on Team, Business, Advanced, and Enterprise plans. It is categorised as a Write tool in the microCMS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the microCMS MCP Server MCP server in PolicyLayer and add a rule for microcms_upload_media: 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 microCMS MCP Server. Nothing to install.
microcms_upload_media is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the microcms_upload_media 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.
Set action: deny in the PolicyLayer policy for microcms_upload_media. 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.
microcms_upload_media is provided by the microCMS MCP Server MCP server (microcmsio/microcms-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from microCMS MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
14 microCMS MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.