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

No annotations are provided, so the description carries the full behavioral burden. It discloses the paid-trial/pricing context, which is genuinely useful, but says nothing about input validity requirements, what happens with a malformed key, or whether the operation is read-only and idempotent.

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 functional content is a single front-loaded sentence with no filler. The '🆓 5 free trial calls' tag is extraneous to the tool's purpose but is short and arguably useful cost context, so it does not seriously damage readability.

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 annotations, no output schema, and two undocumented parameters, the definition is under-specified for an agent to invoke it reliably. Nothing explains the key format, which field to populate, or what the fingerprint response contains.

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% and there are two string parameters, 'key' and 'input', whose relationship is completely unexplained. The description's phrase 'SSH public key' hints at what 'key' means but does nothing to distinguish it from 'input', leaving an agent unable to choose correctly.

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 ('Computes') and resource ('MD5 and SHA256 fingerprints of an SSH public key'), which is unambiguous and distinct from sibling hashing tools like x402-hash or x402-keccak256. An agent can tell what the tool returns without opening the 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?

There is no guidance on when to use this tool versus alternatives, nor any prerequisite mention (e.g., that a full OpenSSH-format public key is expected). The only non-functional sentence is a pricing/trial note ('5 free trial calls per signed wallet'), which is billing, not usage guidance.

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