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

With no annotations the description carries the full burden; it does disclose the return shape (decoded string and length) and an auth/payment context ('per signed wallet'), which is useful. However it says nothing about error behavior for invalid or malformed base64, padding expectations, or what happens if neither input is supplied.

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?

Front-loaded with the action and result in a single efficient sentence; the trailing promo emoji note is extra but short and clearly separated.

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?

For a 2-param tool with no annotations and no output schema, the description covers output and payment context but leaves the data-vs-base64 ambiguity and error behavior unresolved. Adequate but with clear gaps.

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% and neither parameter is documented in the schema, so the description is the only source of meaning. 'From data or base64' hints that the two parameters are alternate input sources, which is valuable, but it is ambiguous about whether they are alternatives or both accepted and adds no format details.

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+resource (decodes base64) and states the output (UTF-8 string and length). 'Decode' distinguishes it from encode siblings like x402-base64, but the description never explicitly names that sibling or its URL-safe variant x402-base64url.

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 x402-base64, x402-base64url, x402-base32 or x402-is-base64. Nothing explains when to pass `data` versus `base64`, which is the core usage decision for a 0-required-param tool.

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