Agent Utils (x402)

by dev.workers.revenue-agent-jw.agent-utils-x402-production

Stablecoin freeze check (Circle USDC/EURC, Tether USDT) + OFAC

stablecoin_blacklist_check

Read-onlyIdempotent

Can this wallet move USDC? Live check of the issuers' own on-chain blacklists: Circle USDC (Base, Ethereum, Arbitrum, Optimism, Polygon, Avalanche), EURC (Base, Ethereum) and Tether USDT (Ethereum), plus OFAC SDN exact match. Up to 20 EVM addresses per call. Returns PASS/BLOCK, which token+chain is frozen, block numbers and contracts read. Fails closed: if a chain cannot be read, 502 (not charged). Errors: 400 invalid address. PAID: $0.001 USDC per call on Base via x402 (MCP transport: retry with params._meta["x402/payment"]). Same tool over plain HTTP: GET /v1/wallet/stablecoin-blacklist.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "address": "<address>"
    },
    "name": "stablecoin_blacklist_check"
  }
}

Input Schema

Name	Required	Description	Default
`address`	Yes	one EVM 0x address, or up to 20 comma-separated

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 10, 2026

TDQS

A4.4/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only/idempotent/open-world, and the description adds substantial unique behavior: batch limit of 20, fail-closed 502 with no charge, 400 on invalid address, exact return payload shape, and the $0.001 x402 payment requirement including the _meta retry key. The payment and fail-closed semantics are things no annotation could convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the decision question and scope, then behavior, then errors and payment — a sensible information hierarchy with no filler. It is dense (payment, errors, HTTP fallback, chains) but each clause carries operationally relevant content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description supplies the return contract (PASS/BLOCK, frozen token+chain, block numbers, contracts read), plus error and failure modes and cost. For a single-parameter read tool, an agent has everything needed to invoke and interpret it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the schema already documents a single 0x address or up to 20 comma-separated ones. The description's 'Up to 20 EVM addresses per call' restates the schema rather than adding format, validation, or edge-case meaning, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific question ('Can this wallet move USDC?') and the exact mechanism: issuer on-chain blacklists for Circle USDC/EURC and Tether USDT, plus OFAC SDN exact match. The enumerated token/chain scope lets an agent tell precisely what is and isn't covered without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The framing question and the explicit coverage list make the intended use case clear, and the plain-HTTP alternative endpoint plus pricing is given. It does not, however, distinguish this from the sibling sanctions_address_check or say when a wallet does NOT need this check.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Agent Utils (x402) tools Inspect

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