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

With no annotations, the description must carry the behavioral burden, and it does disclose meaningful detail: SHA-256 key derivation and the base64 iv/ciphertext/tag return shape. It omits whether output is deterministic per input, how invalid or missing keys are handled, and any rate limits beyond the free-trial mention.

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?

One dense sentence covering algorithm, key derivation, and output format, followed by a short pricing tag. Front-loaded with the operation, though the emoji pricing note is promotional rather than instructive.

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 and no annotations, the description partially compensates by stating the return format, but it leaves four zero-documented parameters ambiguous and gives no guidance on required inputs (required list is empty). Adequate for the operation itself, incomplete for correct invocation.

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% across four parameters, and the description only maps two of them loosely ('text', 'key'). The purpose of 'input' and 'secret' is left entirely unexplained, so an agent cannot tell which field carries the plaintext or whether 'secret' is an alternative to 'key'.

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 description gives a specific verb (Encrypts) and resource (AES-256-GCM) plus the key-derivation scheme, so an agent immediately knows what the tool does. It does not explicitly name the sibling x402-decrypt-aes256gcm, but the encrypt/decrypt distinction is unambiguous from the name.

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 statement of when to use this tool versus alternatives, nor any prerequisite such as needing a matching decrypt call or a key of sufficient length. The only usage-adjacent text is the pricing note about 5 free trial calls per signed wallet.

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