AI agents use fill_forms to create or update resources in PDF Co MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your PDF Co MCP Server environment.
Form filling creates or updates data within PDF documents. This is reversible (can be corrected or regenerated), so it falls under Write rather than Destructive. The empty description reduces confidence slightly, but the name and server context clearly indicate document modification.
From the tool's definition Tool name 'fill_forms' indicates creating or modifying form data. Sibling tools like 'create_fillable_forms' and 'document_to_pdf' show this server performs document manipulation. Form filling modifies document content reversibly.
Documented attack patterns abuse exactly the kind of access fill_forms gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PDF Co MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for fill_forms:
{
"version": "1",
"default": "deny",
"tools": {
"fill_forms": {
"limits": [
{
"counter": "fill_forms_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fill_forms 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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fill_forms. It is categorised as a Write tool in the PDF Co MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the PDF Co MCP Server MCP server in PolicyLayer and add a rule for fill_forms: 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 PDF Co MCP Server. Nothing to install.
fill_forms 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 fill_forms 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 fill_forms. 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.
fill_forms is provided by the PDF Co MCP Server MCP server (pdfdotco/pdfco-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from PDF Co MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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38 PDF Co MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.