Add text highlights to specific text or areas in PDF
AI agents use add_highlights 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 content by adding highlights, which is a reversible annotation. It does not execute code, delete data, or move money. Highlights can be removed, making it Write rather than Destructive. Severity is medium because while the modification is reversible, unmarked or malicious highlights could obscure critical document information, mislead readers, or deface important PDFs.
From the tool's definition 'Add text highlights to specific text or areas in PDF' — modifies PDF by adding visual annotations (highlights) to document content.
Documented attack patterns abuse exactly the kind of access add_highlights 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_highlights:
{
"version": "1",
"default": "deny",
"tools": {
"add_highlights": {
"limits": [
{
"counter": "add_highlights_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_highlights 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 text highlights to specific text or areas in 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_highlights: 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_highlights 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_highlights 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_highlights. 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_highlights 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.