SALT19 Agent Utility Grid

Base Wallet Balance

base-wallet-balance

Idempotent

Read a wallet's live native ETH balance on Base at the latest block without an API key. Price: $0.01 via x402. _salt19_operation_id is recommended but optional for standard x402 compatibility.

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": "base-wallet-balance"
  }
}

Input Schema

Name	Required	Description
`address`	Yes
`_salt19_handoff_id`	No	Optional SALT19 authorization handoff correlation. Preserve the same value across challenge, local signing, and paid retry.
`_salt19_operation_id`	No	Optional but recommended semantic purchase identifier preserved across challenge/payment/retries.
`_x402_payment_signature`	No	Optional x402 payment proof. Omit on the first call; include after satisfying the challenge.

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 1, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Adds valuable behavioral context beyond annotations: the $0.01 x402 price, the no-API-key access path, and live-at-latest-block semantics. The annotation says readOnlyHint=false, but the disclosed payment side effect makes this non-contradictory; idempotent and destructive hints are already annotated.

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 tight, front-loaded sentences with no filler. It states purpose, scope, pricing, and the key optional parameter in the minimum words needed.

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

Completeness3/5

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

Covers purpose, scope, price, and no-API-key access, but does not describe the full x402 challenge/payment flow or the output format/units, and there is no output schema to fill that gap. The schema hints at the challenge flow, but return semantics remain underspecified.

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 already documents three optional protocol parameters with clear descriptions; the description adds that address is the wallet being queried and that _salt19_operation_id is recommended but optional. With 75% schema coverage, it compesates only partially for the undocumented address parameter.

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 verb and resource: 'Read a wallet's live native ETH balance on Base at the latest block'. The 'native ETH' qualifier clearly distinguishes it from sibling token/allowance/state tools, so an agent can select it confidently.

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?

Gives clear context: use when you need a native ETH balance on Base with no API key and are willing to pay via x402. It doesn't name alternatives explicitly, but 'native ETH' implicitly excludes token-balance and transaction-status tools.

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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