s3_upload_file

Upload file to S3 bucket

SERVERNcp SOURCE@portel/ncp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-portel-dev-ncp/s3-upload-file.md

WHAT IT DOES

What s3_upload_file does on Ncp

AI agents use s3_upload_file to create or update resources in Ncp, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ncp environment.

RISK

Why s3_upload_file is rated Medium

S3 uploads are reversible (files can be deleted), so this is Write rather than Destructive. The severity is high because unauthorized uploads could introduce malicious content, overwrite critical files, or consume storage resources, impacting availability and integrity. The confidence is high given the explicit 'upload' action and S3 bucket reference.

From the tool's definition Tool name 's3_upload_file' and description 'Upload file to S3 bucket' indicate this creates or modifies data in cloud storage. Upload operations are Write-category actions.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs s3_upload_file safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Ncp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For s3_upload_file, this is the rule to start with:

s3_upload_file Rate-limited

s3_upload_file 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": {
    "s3_upload_file": {
      "limits": [
        {
          "counter": "s3_upload_file_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 Ncp, apply this rule, and every s3_upload_file call is checked against it from then on.

FAQ

Questions about s3_upload_file

What does the s3_upload_file tool do? +

Upload file to S3 bucket. It is categorised as a Write tool in the Ncp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on s3_upload_file? +

Register the Ncp MCP server in PolicyLayer and add a rule for s3_upload_file: 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 Ncp. Nothing to install.

What risk level is s3_upload_file? +

s3_upload_file is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit s3_upload_file? +

Yes. Add a rate_limit block to the s3_upload_file 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 s3_upload_file completely? +

Set action: deny in the PolicyLayer policy for s3_upload_file. 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 s3_upload_file? +

s3_upload_file is provided by the Ncp MCP server (@portel/ncp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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