Add form fields to an existing PDF
AI agents use add_form_fields to create or update resources in MCP PDF — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP PDF environment.
This tool creates or modifies PDF documents by inserting form fields, which is a reversible write operation. It does not execute arbitrary code, delete data, or move money. The severity is medium because adding form fields could alter document structure or create unintended interactive elements if misused, but the change is reversible and doesn't expose or destroy data irreversibly.
From the tool's definition add_form_fields: 'Add form fields to an existing PDF' — modifies PDF documents by adding interactive form elements
Documented attack patterns abuse exactly the kind of access add_form_fields gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP PDF, and nothing reaches the server without passing your rules. This is the rule we recommend for add_form_fields:
{
"version": "1",
"default": "deny",
"tools": {
"add_form_fields": {
"limits": [
{
"counter": "add_form_fields_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_form_fields 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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Add form fields to an existing PDF. It is categorised as a Write tool in the MCP PDF MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP PDF MCP server in PolicyLayer and add a rule for add_form_fields: 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 MCP PDF. Nothing to install.
add_form_fields 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 add_form_fields 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 add_form_fields. 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.
add_form_fields is provided by the MCP PDF MCP server (rsp2k/mcp-pdf). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP PDF, 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.
46 MCP PDF tools catalogued and risk-classified — across an index of 43,000+ MCP servers.