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ERC-20 Balance (Multicall)

erc20_balance
Read-only

Balances of up to 20 arbitrary ERC-20 tokens for one wallet in a single Multicall3 round-trip: raw and decimal-formatted balance, decimals and symbol per token, on Base, Ethereum, BSC, Polygon, Arbitrum or Optimism. Pay per call with USDC or USDT on Base via x402. 3 free calls per wallet.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
chainNobase (default), ethereum, bsc, polygon, arbitrum, optimism.
walletNoYour EVM wallet address (0x...). Unlocks the free tier (3 free calls per wallet).
api_keyNoOptional AMR enterprise API key.
x_paymentNoOptional signed x402 payment payload (base64 JSON) for USDC/USDT on Base.
wallet_addressYesEVM wallet address.
contract_addressesYes1-20 ERC-20 contract addresses.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
chainYes
tokenNoToken actually used for payment (USDC, USDT or FREE).USDC
sourceYes
tokensYes
routingYesHow the request was routed (provider, fallback, cache, latency).
chain_idYes
cost_usdcYesPrice charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.
fetched_atNoUTC timestamp when the data was fetched.
token_countYes
block_numberYes
wallet_addressYes
freshness_secondsYesAge of the underlying data in seconds (0 = fetched live).
x_payment_responseNoBase64-encoded x402 settlement receipt (mirrors the X-PAYMENT-RESPONSE header). Only present when the call was paid with `x_payment`.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "description": "Response for ``POST /erc20-balance``.",
      +  "properties": {
      +    "block_number": {
      +      "title": "Block Number",
      +      "type": "integer"
      +    },
      +    "chain": {
      +      "title": "Chain",
      +      "type": "string"
      +    },
      +    "chain_id": {
      +      "title": "Chain Id",
      +      "type": "integer"
      +    },
      +    "cost_usdc": {
      +      "description": "Price charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.",
      +      "title": "Cost Usdc",
      +      "type": "number"
      +    },
      +    "fetched_at": {
      +      "description": "UTC timestamp when the data was fetched.",
      +      "format": "date-time",
      +      "title": "Fetched At",
      +      "type": "string"
      +    },
      +    "freshness_seconds": {
      +      "description": "Age of the underlying data in seconds (0 = fetched live).",
      +      "title": "Freshness Seconds",
      +      "type": "integer"
      +    },
      +    "routing": {
      +      "description": "How the request was routed (provider, fallback, cache, latency).",
      +      "properties": {
      +        "cache_hit": {
      +          "default": false,
      +          "description": "True if the result was served from cache.",
      +          "title": "Cache Hit",
      +          "type": "boolean"
      +        },
      +        "fallback_used": {
      +          "default": false,
      +          "description": "True if the primary provider failed and a fallback served the result.",
      +          "title": "Fallback Used",
      +          "type": "boolean"
      +        },
      +        "latency_ms": {
      +          "default": 0,
      +          "description": "End-to-end routing latency in milliseconds.",
      +          "title": "Latency Ms",
      +          "type": "integer"
      +        },
      +        "provider": {
      +          "description": "Name of the upstream provider that served the result.",
      +          "title": "Provider",
      +          "type": "string"
      +        },
      +        "providers_tried": {
      +          "description": "Providers attempted, in order.",
      +          "items": {
      +            "type": "string"
      +          },
      +          "title": "Providers Tried",
      +          "type": "array"
      +        }
      +      },
      +      "required": [
      +        "provider"
      +      ],
      +      "title": "RoutingMeta",
      +      "type": "object"
      +    },
      +    "source": {
      +      "title": "Source",
      +      "type": "string"
      +    },
      +    "token": {
      +      "default": "USDC",
      +      "description": "Token actually used for payment (USDC, USDT or FREE).",
      +      "title": "Token",
      +      "type": "string"
      +    },
      +    "token_count": {
      +      "title": "Token Count",
      +      "type": "integer"
      +    },
      +    "tokens": {
      +      "items": {
      +        "properties": {
      +          "balance": {
      +            "anyOf": [
      +              {
      +                "type": "number"
      +              },
      +              {
      +                "type": "null"
      +              }
      +            ],
      +            "default": null,
      +            "title": "Balance"
      +          },
      +          "contract": {
      +            "title": "Contract",
      +            "type": "string"
      +          },
      +          "decimals": {
      +            "anyOf": [
      +              {
      +                "type": "integer"
      +              },
      +              {
      +                "type": "null"
      +              }
      +            ],
      +            "default": null,
      +            "title": "Decimals"
      +          },
      +          "error": {
      +            "anyOf": [
      +              {
      +                "type": "string"
      +              },
      +              {
      +                "type": "null"
      +              }
      +            ],
      +            "default": null,
      +            "title": "Error"
      +          },
      +          "raw": {
      +            "anyOf": [
      +              {
      +                "type": "string"
      +              },
      +              {
      +                "type": "null"
      +              }
      +            ],
      +            "default": null,
      +            "title": "Raw"
      +          },
      +          "symbol": {
      +            "anyOf": [
      +              {
      +                "type": "string"
      +              },
      +              {
      +                "type": "null"
      +              }
      +            ],
      +            "default": null,
      +            "title": "Symbol"
      +          }
      +        },
      +        "required": [
      +          "contract"
      +        ],
      +        "title": "Erc20TokenBalance",
      +        "type": "object"
      +      },
      +      "title": "Tokens",
      +      "type": "array"
      +    },
      +    "wallet_address": {
      +      "title": "Wallet Address",
      +      "type": "string"
      +    },
      +    "x_payment_response": {
      +      "description": "Base64-encoded x402 settlement receipt (mirrors the X-PAYMENT-RESPONSE header). Only present when the call was paid with `x_payment`.",
      +      "type": "string"
      +    }
      +  },
      +  "required": [
      +    "freshness_seconds",
      +    "cost_usdc",
      +    "routing",
      +    "wallet_address",
      +    "chain",
      +    "chain_id",
      +    "block_number",
      +    "tokens",
      +    "token_count",
      +    "source"
      +  ],
      +  "type": "object"
      +}
  2. Changed1 schema field changed
    • changedInput schema / properties / wallet / description
      Previous value: -"Your EVM wallet address (0x...). Unlocks the free tier (3 calls per wallet)."New value: +"Your EVM wallet address (0x...). Unlocks the free tier (3 free calls per wallet)."
  3. Added

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description adds meaningful context: Multicall3 batching, supported chains, the x402 payment mechanism, and the 3-free-calls-per-wallet limit. There is no contradiction between the description and the annotations.

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

Conciseness5/5

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

Two sentences are packed with high-signal information: return contents, token scope, multicall batching, supported chains, payment options, and free tier. The core purpose is front-loaded and no filler is present.

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

Completeness4/5

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

The description covers the essential calling context: what is returned, how many tokens, which chains, and how to pay. Since an output schema exists, return-value details are handled structurally; the only slight gap is explicit when-to-use/alternative routing among the many balance- and price-related siblings.

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?

The input schema already documents all six parameters with 100% coverage, so the description does not need to compensate. It reinforces useful constraints like 1-20 contract addresses and one-wallet scope, but it does not clarify the distinction between 'wallet' and 'wallet_address' beyond what the schema already says.

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?

The description opens with a specific verb ('Balances') and names the exact resource: up to 20 arbitrary ERC-20 tokens for one wallet, including raw and decimal-formatted balances, decimals, and symbols. Saying 'arbitrary ERC-20 tokens' and 'one wallet' clearly distinguishes it from sibling tools like wallet_balance or token_price.

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 description clearly implies use for batched ERC-20 balance checks for a single wallet in one multicall round-trip, and it adds payment/free-tier context. It does not explicitly say when not to use it or name alternatives such as wallet_balance or token_price, so it stops just short of full routing guidance.

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

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