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

Annotations already declare this readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds information the annotations do not carry: a daily quota counted per caller, that payment/auth headers (X-Payment, X-Payment-Tx, Bearer fg_…) must go in MCP request headers and not in the parameters, and the fields returned. A statement of error/limit behavior when quota is hit would push this higher.

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?

The useful content is front-loaded, but the same facts (free tier, args, quota) are stated three times across the English summary, Chinese summary, and the [zh]/[en] vendor block. The payment-header note is valuable but buried at the end. Removing the duplicated free/args statements would tighten it substantially.

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-only lookup with no output schema, the description covers most of what an agent needs: what checks are returned, that it is free with a per-caller quota, and how payment credentials are transmitted out-of-band. The remaining hole is how to specify the chain and what the risk codes signify, which the schema does not fill either.

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 0%, so the description must compensate for two bare string parameters. It only repeats 'Args: address, chain' with no semantics — no accepted chain identifiers or default behavior when chain is omitted, and no address format expectations. This is a real gap for a chain-scoped lookup.

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 states a specific resource and enumerates the concrete outputs: whether it is a contract, code size, token standard and symbol, proxy upgradeability, and risk signal codes. That is far more than a restatement of the name and lets an agent predict the response. It stops short of 5 because it never names a sibling such as contract-fingerprint.audit to delimit scope.

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 signals that this is the free, lightweight peek and that there is a per-caller daily quota, which implies a cheaper alternative exists for deeper work. However, it never explicitly says when to prefer this over contract-fingerprint.audit or what to do once the free quota is exhausted. Usage is therefore implied rather than stated.

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