Check your USDC balance on MailerAstro. This is FREE — no payment required. Use this before sending emails to verify you have sufficient funds. Your wallet address is your identity on MailerAstro. Args: - wallet_address (string): Your 0x... Ethereum/Base wallet address - response_format ('json' |...
Part of the MailerAstro server.
Free to start. No card required.
AI agents call mailerastro_check_balance to retrieve information from MailerAstro 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 mailerastro_check_balance 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.
{
"version": "1",
"default": "deny",
"tools": {
"mailerastro_check_balance": {}
}
}See the full MailerAstro policy for all 6 tools.
These attack patterns abuse exactly the kind of access mailerastro_check_balance gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Check your USDC balance on MailerAstro. This is FREE — no payment required. Use this before sending emails to verify you have sufficient funds. Your wallet address is your identity on MailerAstro. Args: - wallet_address (string): Your 0x... Ethereum/Base wallet address - response_format ('json' | 'markdown'): Output format (default: 'json') Returns: JSON with: walletAddress, balance (in USD), currency, lastUpdated Examples: - Check balance: wallet_address="0x1234...abcd" - A balance of $1.00 can send ~1,000 plain text emails or ~200 HTML emails Error Handling: - 404: Wallet not found. Send your first email to auto-register, or fund your wallet with USDC on Base.. It is categorised as a Read tool in the MailerAstro MCP Server, which means it retrieves data without modifying state.
Register the MailerAstro MCP server in PolicyLayer and add a rule for mailerastro_check_balance: 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 MailerAstro. Nothing to install.
mailerastro_check_balance 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 mailerastro_check_balance 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 mailerastro_check_balance. 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.
mailerastro_check_balance is provided by the MailerAstro MCP server (mailerastro/mailerastro-email). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 6 MailerAstro tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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