Fill a PDF form with provided data and save it. output_path may be the same as pdf_path for in-place editing; the original is backed up on the first same-path mutation. All paths must be absolute paths on the user
AI agents use fill_pdf to create or update resources in PDF Tools — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your PDF Tools environment.
This tool modifies files by populating form fields and persisting changes. While reversible (backups are maintained), it writes data to disk. The severity is medium because misuse could overwrite user data in PDF files, but the impact is limited to local files and the action is reversible via backup.
From the tool's definition Tool "fills a PDF form with provided data and save it" and explicitly mentions "in-place editing"; these are write operations that create or modify data. The description confirms data is persisted ("save it").
Documented attack patterns abuse exactly the kind of access fill_pdf gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PDF Tools, and nothing reaches the server without passing your rules. This is the rule we recommend for fill_pdf:
{
"version": "1",
"default": "deny",
"tools": {
"fill_pdf": {
"limits": [
{
"counter": "fill_pdf_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fill_pdf 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.
Fill a PDF form with provided data and save it. output_path may be the same as pdf_path for in-place editing; the original is backed up on the first same-path mutation. All paths must be absolute paths on the user. It is categorised as a Write tool in the PDF Tools MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the PDF Tools MCP server in PolicyLayer and add a rule for fill_pdf: 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 Tools. Nothing to install.
fill_pdf 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_pdf 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_pdf. 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_pdf is provided by the PDF Tools MCP server (open-document-alliance/pdf-tools). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 36 PDF Tools tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
36 PDF Tools tools catalogued and risk-classified — across an index of 42,500+ MCP servers.