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

Adds behavior beyond the annotations: explicit return formats (hex and base64) and, importantly, a per-call cost of $0.001 USDC on Base paid via x402, which is critical for an agent deciding whether to call. It does not explain error behavior or why readOnlyHint/idempotentHint are false for a deterministic digest operation.

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?

Two sentences, zero filler, with the core purpose and algorithm/encoding details front-loaded ahead of the usage and pricing notes.

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?

With no output schema, the description compensates by naming the return encodings, and it discloses the payment requirement. Minor omissions remain around failure modes and cost/limit behavior, but nothing essential to invoking it correctly is missing.

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 are already documented; the description only restates the algorithm set and default. Baseline 3 applies since the schema carries the parameter semantics.

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 (hash), the input type (UTF-8 text), the supported algorithms with the default, and the output encodings. An agent can tell this apart from sibling hmac (keyed) and base64_encode (encoding) without opening either schema.

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 concrete intended uses (checksums, cache keys, deduplication), which is clear context for selection. It does not name alternatives such as hmac for keyed hashing or state when not to use it, so it stops short of full when/when-not guidance.

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