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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds the crucial cost context ('Paid $0.004 USDC on Base or Solana') and specifies the exact hash variant, but it does not disclose other behavioral aspects like rate limits or payment mechanics. No contradiction with annotations is present.

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?

A single sentence conveys all essential information: payment, network, algorithm, and input types. It is concise and without waste, though the payment detail is front-loaded before the core purpose, which is slightly unconventional but not detrimental.

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 simple hash tool with no output schema, the description covers the core operation and payment cost, but it omits any mention of error cases, payment methods, or whether the result is returned in a specific format. The absence of an output schema and the paid nature suggest a need for a bit more context, though the tool is straightforward enough that a 3 is appropriate.

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. It clarifies that 'input' can be UTF-8 text or hex bytes, directly mapping to the 'encoding' enum (utf8/hex). This adds meaning beyond the bare schema, even though it does not detail maxLength or the required flag, which are structural.

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 clearly states the tool computes an 'exact Ethereum keccak256 digest' for UTF-8 text or hex bytes, which is a specific verb+resource. It differentiates from sibling hash tools like sha256/sha512 by naming the algorithm and its Ethereum-specific nature, though it does not explicitly name those alternatives.

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?

The description implies usage for keccak256 hashing but provides no explicit guidance on when to choose this tool over alternatives such as sha256, sha512, or hash_encode. There is no mention of when not to use it or what conditions select a sibling tool, leaving the agent to infer suitability.

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