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

No annotations exist, so the description carries the full behavioral burden. It discloses the input encoding (base64), the key-derivation scheme (SHA-256), and a trial/pricing constraint (5 free calls per signed wallet), but says nothing about failure modes on a bad auth tag, whether the key is supplied raw or derived from secret, or what the output looks like.

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?

It is a single front-loaded sentence, which is good, but the trailing emoji and trial-marketing clause dilute a technical definition. Reasonably sized, though the promotional tail does not help an agent call the tool.

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, 0 required parameters, and 0% schema coverage, the description should specify the required call shape and result behavior. It instead leaves the agent unsure which of the five inputs are mandatory and what a successful or failed decrypt returns.

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 0% across 5 parameters, so the description must compensate. It mentions the key, IV, auth tag, and ciphertext components but does not map them to parameter names, and the fifth parameter 'secret' (and its relationship to 'key') is never explained, leaving the required call shape ambiguous.

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 (Decrypts) and resource (base64 AES-256-GCM ciphertext via SHA-256 derived key), which is far more precise than a tautology. However, it does not name or contrast with the obvious sibling x402-encrypt-aes256gcm, so sibling differentiation is left implicit.

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 when-to-use, when-not-to-use, or alternative guidance. The agent is told what the tool does but not the conditions under which it should be selected over the encrypt counterpart or other crypto tools.

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