List valid constants for tool parameters.
AI agents call list_tool_constants to retrieve information from A Share without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a utility tool for discovering valid input values (constants/enums) for other tools' parameters. It is purely informational—it reads and returns reference data with no side effects, no code execution, and no data modification. This is characteristic of a Read category tool with low severity since misuse cannot cause harm beyond information disclosure.
From the tool's definition Tool name 'list_tool_constants' and description 'List valid constants for tool parameters' indicate a query operation that retrieves metadata about valid parameter values without modifying or executing any operations.
Documented attack patterns abuse exactly the kind of access list_tool_constants gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and A Share, and nothing reaches the server without passing your rules. This is the rule we recommend for list_tool_constants:
{
"version": "1",
"default": "deny",
"tools": {
"list_tool_constants": {}
}
}list_tool_constants is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List valid constants for tool parameters. It is categorised as a Read tool in the A Share MCP Server, which means it retrieves data without modifying state.
Register the A Share MCP server in PolicyLayer and add a rule for list_tool_constants: 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 A Share. Nothing to install.
list_tool_constants is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_tool_constants 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 list_tool_constants. 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.
list_tool_constants is provided by the A Share MCP server (shouldnotappearcalm/a-share-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from A Share, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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55 A Share tools catalogued and risk-classified — across an index of 43,000+ MCP servers.