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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior: determinism of the output and the per-call x402/USDC payment requirement, which no annotation conveys. It stops short of describing output length or payment-failure behavior.

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?

Three short sentences, front-loaded with what the tool does, then output form, then use case, then payment mechanics. Nothing is padded or repeated from the schema.

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 fortunately states the return form (hex digest), and it covers the unusual payment flow that an agent must know to avoid a failed call. Minor gaps remain on digest length and error/payment-required behavior, but nothing blocking.

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 50%: _payment is documented in the schema, while 'input' is only typed. The description compensates partially by clarifying that input is an arbitrary string and that the result is a hex digest, but adds no encoding, size limit, or empty-input semantics. Baseline 3 when schema does part of the work.

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?

Specific verb plus resource (SHA-512 hash of an input string, hex digest output) with the algorithm named explicitly, which separates it from hash_sha256 and hash_hmac among siblings. It does not call out those siblings by name, but the algorithm alone is distinct enough for selection.

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 phrase 'for checksums and fingerprints' implies the intended use, but there is no explicit when-to-use versus hash_sha256/hash_hmac, no exclusion guidance, and no mention of when a hash is inappropriate (e.g. passwords). Usage is inferable, not stated.

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