Upload a file attachment to a ServiceNow record. The file content must be
AI agents use upload_attachment to create or update resources in Now Sdk Ext — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Now Sdk Ext environment.
Uploading an attachment is a write operation—it creates or adds new data to an existing record reversibly. The tool modifies the state of a ServiceNow record by attaching a file. While not destructive (attachments can be removed), it does alter system state.
From the tool's definition Tool is named 'upload_attachment' and described as 'Upload a file attachment to a ServiceNow record.' This creates new data (a file attachment) in a ServiceNow instance without deleting or overwriting existing records.
Documented attack patterns abuse exactly the kind of access upload_attachment gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Now Sdk Ext, and nothing reaches the server without passing your rules. This is the rule we recommend for upload_attachment:
{
"version": "1",
"default": "deny",
"tools": {
"upload_attachment": {
"limits": [
{
"counter": "upload_attachment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}upload_attachment 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.
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Upload a file attachment to a ServiceNow record. The file content must be. It is categorised as a Write tool in the Now Sdk Ext MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Now Sdk Ext MCP server in PolicyLayer and add a rule for upload_attachment: 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 Now Sdk Ext. Nothing to install.
upload_attachment 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 upload_attachment 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 upload_attachment. 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.
upload_attachment is provided by the Now Sdk Ext MCP server (sonisoft-cnanda/now-sdk-ext-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Now Sdk Ext, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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86 Now Sdk Ext tools catalogued and risk-classified — across an index of 43,000+ MCP servers.