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

Annotations already cover read-only, non-destructive, open-world and non-idempotent behavior, and the description reinforces them with real detail: pending vs confirmed scope, a 400 rejection for malformed addresses that is explicitly uncharged, and per-call pricing including free failures, which explains why idempotentHint=false matters. It stops short of saying how confirmed and pending counts are returned (one value or two), leaving a small behavioral gap.

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?

Front-loaded with purpose and use cases, then validation, example, and pricing. The pricing message is stated twice ("first 25 free; failed calls free" and "each call is charged, so repeats are not free"), which is mild redundancy but each sentence still carries actionable information.

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 one-parameter read tool with no output schema, the description covers purpose, alternatives, error handling, and cost. The main missing piece is the return shape for the confirmed versus pending counts, which an agent would need to interpret the response.

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?

With a single parameter at 100% schema coverage, the baseline is 3; the description adds a concrete valid address example and the validation behavior for malformed input, which is meaning the schema does not carry. It does not add further format constraints (e.g. checksum requirements), so it is not a 5.

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 ("Read the transaction count (nonce)") scoped to a named chain (zkSync Era) and a specific input shape (0x address). It also distinguishes itself from the sibling zksync_balance, so an agent can separate the two without inspecting schemas.

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?

Gives two concrete use cases ("build the next transaction" and "tell whether an address has ever sent anything") and explicitly redirects balance lookups to zksync_balance. The when-to-use and the alternative are both stated.

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