Agent Margin Router

Wallet Balance

wallet_balance

Read-only

Native + stablecoin balances (ETH, USDC, USDT, DAI, WETH) of any EVM wallet with USD valuation, read directly from public RPC nodes on Base, Ethereum, Arbitrum, Optimism or Polygon. No API key. Pay per call with USDC or USDT on Base via x402. 3 free calls per wallet.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`chain`	No	base \| ethereum \| arbitrum \| optimism \| polygon (default base).	base
`tokens`	No	Token symbols, default all known (USDC, USDT, DAI, WETH).
`wallet`	No	Your EVM wallet address (0x...). Unlocks the free tier (3 free calls per wallet).
`address`	Yes	EVM address (0x + 40 hex chars).
`api_key`	No	Optional AMR enterprise API key.
`x_payment`	No	Optional signed x402 payment payload (base64 JSON) for USDC/USDT on Base.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`chain`	Yes
`token`	No	Token actually used for payment (USDC, USDT or FREE).	USDC
`address`	Yes
`routing`	Yes	How the request was routed (provider, fallback, cache, latency).
`balances`	Yes
`chain_id`	Yes
`cost_usdc`	Yes	Price charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.
`total_usd`	Yes
`fetched_at`	No	UTC timestamp when the data was fetched.
`block_number`	Yes
`freshness_seconds`	Yes	Age of the underlying data in seconds (0 = fetched live).
`x_payment_response`	No	Base64-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.

Changed1 schema field changedSep 15, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "description": "Response for ``POST /wallet-balance``.",
+  "properties": {
+    "address": {
+      "title": "Address",
+      "type": "string"
+    },
+    "balances": {
+      "additionalProperties": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "title": "Balances",
+      "type": "object"
+    },
+    "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"
+    },
+    "token": {
+      "default": "USDC",
+      "description": "Token actually used for payment (USDC, USDT or FREE).",
+      "title": "Token",
+      "type": "string"
+    },
+    "total_usd": {
+      "title": "Total Usd",
+      "type": "number"
+    },
+    "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": [
+    "address",
+    "chain",
+    "chain_id",
+    "block_number",
+    "balances",
+    "total_usd",
+    "freshness_seconds",
+    "cost_usdc",
+    "routing"
+  ],
+  "type": "object"
+}

Changed2 schema fields changedSep 13, 2026

addedInput schema / properties / chain / default
```
Added value: +"base"
```

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)."

First observedSep 11, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Beyond the readOnlyHint/openWorldHint annotations, the description adds valuable behavioral context: it reads directly from public RPC nodes (no centralized API), has a payment mechanism via x402 (cost implications), and includes a free tier. No contradictions with 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 dense sentence clusters plus a payment/free-tier sentence, with zero filler. The main purpose is front-loaded, and each sentence contributes functional or behavioral info needed for correct invocation.

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?

Given the tool has a rich output schema and read-only annotations, the description covers all needed invocation details: target addresses, chains, token scope, rate limits, payment requirements, and no-key access. Nothing critical is missing for an agent to call 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 coverage is 100%, so the input schema already documents all six parameters. The description restates a few parameter-related details (chain options, wallet free-trip trigger) but adds marginal meaning beyond the schema baseline, justifying the default score of 3.

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 clearly states a specific verb (reads) and resource (native + stablecoin balances of any EVM wallet) with USD valuation, on multiple chains. It is distinct from siblings like erc20_balance and token_price by naming the specific token set (ETH, USDC, USDT, DAI, WETH) and multi-chain scope.

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?

It gives clear usage context: no API key, pay per call on Base, 3 free calls per wallet, and direct RPC read. It doesn't explicitly name alternative tools or exclusion criteria, but the conditions under which to use it are conveyed well enough for a disambiguated selection.

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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