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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context on top: it is pure local computation with no chain interaction, priced at $0.002/call over x402 on Base, free one call/day, and accepts a prepaid x-credit-token header with no API key. Payment, auth, and rate-limit behavior are all disclosed.

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 operative facts are front-loaded in the first two sentences, but the description is padded with promotional filler ('the most-bought x402 utility,' 'the commodity hashing call the whole x402 ecosystem hammers, served at the floor') and an irrelevant 'Not financial advice' for a pure hashing tool. The pricing/auth sentences do earn their place, so the waste is moderate rather than severe.

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 compute tool with an output schema and full annotation coverage, the description supplies everything an agent needs: input encoding, algorithm choice, cost, and auth model. Return values need not be explained because an output schema exists; only minor noise reduces it below a 5.

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%, so both parameters (input, algo) are already documented in the schema and the description largely restates them ('keccak256 (default) or sha256'). It adds marginal value by explaining what kinds of values are hashed (event topics, selectors, mapping keys), but does not go beyond the schema in any meaningful syntax or format detail.

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 first sentence gives a specific verb and resource: 'Compute keccak256 ... or sha256 of any input,' naming the exact algorithms and the EVM use cases (event topics, function selectors, mapping keys). However, it never differentiates itself from nearby siblings like encode_selector or decode_selector, which also deal with selectors and could be confused with this tool.

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 states the input encoding rule (input=text for UTF-8, 0x-hex for raw bytes) and the algorithm default, and frames the context as 'pure compute, no chain.' It never states when to prefer this over alternatives such as encode_selector/decode_selector, so there is no exclusion guidance.

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