chain_nonce

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

Annotations already declare readOnlyHint/idempotentHint/openWorldHint, so the description goes further by disclosing the paywall: x402 USDC on Base, free with an API key, and that a bare HTTP 402 carries a price quote rather than a failure. That last point is genuinely useful behavioral context an agent could otherwise misread as an error, though failure modes for an unresolvable ENS name or bad chain are not described.

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

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

Purpose and usage are front-loaded before the example and pricing details, and every sentence is on-topic. The pricing sentence is slightly long relative to its value, but it earns its place because the 402 behavior is counterintuitive.

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

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

For a two-parameter read tool with no output schema, the definition covers what is returned at a conceptual level (confirmed plus pending nonce) and explains the payment path. It does not name the response field names, which would be the remaining gap for an agent parsing the result.

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

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

Schema description coverage is 100%, documenting both address (0x or ENS) and chain (with the five supported values and base default), so the description need not repeat them. The worked example reinforces the shape of a call but adds no new constraint beyond the schema — baseline 3.

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

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

States a specific verb and resource — transaction count (nonce) for an address or ENS name — and specifies that both confirmed and pending nonces are returned. The phrase 'Not for balances' explicitly separates it from chain_balance and chain_token_balance among the siblings.

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

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

'Use when you need an address's confirmed and pending transaction count before building a transaction' gives a clear triggering condition, and 'Not for balances' gives an exclusion. It stops short of naming the specific alternative tool (chain_balance) the way an ideal definition would, but the intent is unambiguous.

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