Buy credits for the edge library and AI research. Default $5 minimum. Free — no credits consumed to call this. TWO PAYMENT METHODS: card (default): Returns a Stripe Checkout link for your user to click and pay. After payment, call check_balance to confirm credits were added. crypto: USDC on Base....
Part of the VARRD — Statistically Validated Trading Edges + AI Research Engine server.
Free to start. No card required.
AI agents use buy_credits to create or modify resources in VARRD — Statistically Validated Trading Edges + AI Research Engine. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call buy_credits repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach VARRD — Statistically Validated Trading Edges + AI Research Engine.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"buy_credits": {
"limits": [
{
"counter": "buy_credits_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full VARRD — Statistically Validated Trading Edges + AI Research Engine policy for all 9 tools.
These attack patterns abuse exactly the kind of access buy_credits gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Buy credits for the edge library and AI research. Default $5 minimum. Free — no credits consumed to call this. TWO PAYMENT METHODS: card (default): Returns a Stripe Checkout link for your user to click and pay. After payment, call check_balance to confirm credits were added. crypto: USDC on Base. Fully autonomous — no human needed. Three steps: 1. buy_credits(payment_method='crypto') → returns deposit address + payment_intent_id 2. Send USDC to the deposit address (use your wallet tool) 3. buy_credits(payment_intent_id='pi_...') → confirms payment, credits added instantly If you have wallet access, this is the fastest path — fully machine-to-machine.. It is categorised as a Write tool in the VARRD — Statistically Validated Trading Edges + AI Research Engine MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the VARRD — Statistically Validated Trading Edges + AI Research Engine MCP server in PolicyLayer and add a rule for buy_credits: 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 VARRD — Statistically Validated Trading Edges + AI Research Engine. Nothing to install.
buy_credits 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 buy_credits 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 buy_credits. 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.
buy_credits is provided by the VARRD — Statistically Validated Trading Edges + AI Research Engine MCP server (https://app.varrd.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 9 VARRD — Statistically Validated Trading Edges + AI Research Engine tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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