Create a signed URL for client-side file uploads without exposing your API key
AI agents use createSignedUploadUrl to create or update resources in Pinata MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Pinata MCP environment.
This tool facilitates file uploads to IPFS via a pre-signed URL mechanism. While the upload itself is delegated to the client, the tool's primary function is to enable write operations by provisioning authenticated access.
From the tool's definition Tool creates a signed URL for 'client-side file uploads', enabling data to be written to IPFS storage. The description explicitly states it's for 'uploads', which modifies/adds data to the system.
Documented attack patterns abuse exactly the kind of access createSignedUploadUrl gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pinata MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for createSignedUploadUrl:
{
"version": "1",
"default": "deny",
"tools": {
"createSignedUploadUrl": {
"limits": [
{
"counter": "createsigneduploadurl_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}createSignedUploadUrl 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.
Create a signed URL for client-side file uploads without exposing your API key. It is categorised as a Write tool in the Pinata MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Pinata MCP server in PolicyLayer and add a rule for createSignedUploadUrl: 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 Pinata MCP. Nothing to install.
createSignedUploadUrl 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 createSignedUploadUrl 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 createSignedUploadUrl. 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.
createSignedUploadUrl is provided by the Pinata MCP server (pinatacloud/pinata-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Pinata MCP, 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.
35 Pinata MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.