Add validation rules to existing form fields
AI agents use add_field_validation 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 modifies form fields by applying validation rules—a write operation that can be undone or modified later. It does not execute code, delete data, or create financial obligations. While it could be misused to make forms reject valid input, the core action is reversible Write.
From the tool's definition Tool name 'add_field_validation' and description 'Add validation rules to existing form fields' indicate modification of form field properties.
Documented attack patterns abuse exactly the kind of access add_field_validation 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_field_validation:
{
"version": "1",
"default": "deny",
"tools": {
"add_field_validation": {
"limits": [
{
"counter": "add_field_validation_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_field_validation 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.
Add validation rules to existing form fields. 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_field_validation: 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_field_validation 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_field_validation 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_field_validation. 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_field_validation 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.