Low Risk

list_topup_tiers

Lists the available prepaid-credit top-up tiers, the USD amount each tier charges over x402, and the bonus credit percentage on each. Use this before calling topup_credits to pick the right tier. Free, no API key required.

Part of the TRIALPATH server.

list_topup_tiers is read-only, but an agent in a loop can still rack up calls and cost. PolicyLayer caps every call before it runs. Live in minutes.

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AI agents call list_topup_tiers to retrieve information from TRIALPATH without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.

Even though list_topup_tiers only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.

Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.

policy.json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_topup_tiers": {}
  }
}

See the full TRIALPATH policy for all 14 tools.

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These attack patterns abuse exactly the kind of access list_topup_tiers gives an agent. Each links to the full case and the policy that stops it:

Browse the full MCP Attack Database →

Every attack above starts with a tool call. PolicyLayer checks each one against your policy first, so list_topup_tiers only ever does what you allow.

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Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.

What does the list_topup_tiers tool do? +

Lists the available prepaid-credit top-up tiers, the USD amount each tier charges over x402, and the bonus credit percentage on each. Use this before calling topup_credits to pick the right tier. Free, no API key required.. It is categorised as a Read tool in the TRIALPATH MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_topup_tiers? +

Register the TRIALPATH MCP server in PolicyLayer and add a rule for list_topup_tiers: 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 TRIALPATH. Nothing to install.

What risk level is list_topup_tiers? +

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

Can I rate-limit list_topup_tiers? +

Yes. Add a rate_limit block to the list_topup_tiers 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 list_topup_tiers completely? +

Set action: deny in the PolicyLayer policy for list_topup_tiers. 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 list_topup_tiers? +

list_topup_tiers is provided by the TRIALPATH MCP server (spencerdgarrett/TRIALPATH). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every TRIALPATH tool call.

Deterministic rules across all 14 TRIALPATH tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.

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