hover

THE RISK

Low Risk

Why hover needs a policy

This tool retrieves and displays informational content (documentation, type hints) at a specified location in code. It has no side effects and only reads/queries data from the language server, making it a pure Read operation with minimal risk.

From the tool's definition Display documentation, type hints, or other hover information for a given location

Documented attack patterns abuse exactly the kind of access hover gives an agent:

POLICY

How to control hover

PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Language Server, and nothing reaches the server without passing your rules. This is the rule we recommend for hover:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "hover": {}
  }
}

hover is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register MCP Language Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More MCP Language Server tools

Write edit_file Allows making multiple text edits to a file based on line numbers. Provides a more reliabl Write rename_symbol Rename a symbol across a project. Read definition Retrieves the complete source code definition of any symbol (function, type, constant, etc Read diagnostics Provides diagnostic information for a specific file, including warnings and errors. Read references Locates all usages and references of a symbol throughout the codebase.

All 6 MCP Language Server tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about hover

What does the hover tool do? +

Display documentation, type hints, or other hover information for a given location. It is categorised as a Read tool in the MCP Language Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on hover? +

Register the MCP Language Server MCP server in PolicyLayer and add a rule for hover: 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 Language Server. Nothing to install.

What risk level is hover? +

hover is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit hover? +

Yes. Add a rate_limit block to the hover 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.

How do I block hover completely? +

Set action: deny in the PolicyLayer policy for hover. 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.

What MCP server provides hover? +

hover is provided by the MCP Language Server MCP server (isaacphi/mcp-language-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Language Server tool call.

Start from MCP Language Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →