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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful non-annotation context: pricing ($0.01/call, first 25 free, failed calls free) and an explicit failure code for non-ERC-20 input. However it does not explain the unusual idempotentHint=false — it says repeats are charged, which is a billing fact rather than whether repeated identical calls return the same data.

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?

Well front-loaded: purpose first, then use cases, then input format, then pricing. Slightly over-packed — the cost story is stated three times in different forms ("$0.01/call", "each call is charged, so repeats are not free", "failed calls free"), which is mild redundancy in an otherwise dense, waste-free paragraph.

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?

There is no output schema, and the description compensates by enumerating the returned fields (name, symbol, decimals, total supply). For a one-parameter read tool that is essentially complete; the only remaining gap is whether the response is wrapped in a result/metadata envelope or how ticks are resolved when a ticker is ambiguous across chains.

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 coverage is 100% and the single `token` parameter already documents the ticker-or-0x-address union, so the schema carries the load; the baseline of 3 applies. The description adds a concrete example address and the error semantics for an address that is not an ERC-20 contract, which is marginal extra value rather than new parameter syntax.

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?

The description names a specific verb ("look up") and a specific resource set (name, symbol, decimals, total supply) on a specific chain (zkSync Era ERC-20 contracts), and explicitly separates itself from zksync_token_balance. An agent can distinguish this from the dozens of sibling *_token_info tools purely by the chain prefix plus this sentence.

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?

It gives two positive use cases (identifying an unknown token address, formatting raw amounts) and one explicit exclusion with the named alternative ("for a holder's balance use zksync_token_balance"). Failure routing is also specified: a non-ERC-20 address returns 422 and is uncharged, so the agent knows the error is expected rather than fatal.

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