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

With no annotations, the description carries the full burden of behavioral disclosure. It adds pricing/trial context ('FREE utility', '5 free trial calls per signed wallet') but does not disclose return format, failure behavior, case sensitivity, or whether any side effects or authentication are involved. This is minimal behavioral transparency for an unannotated tool.

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 core purpose is stated in a single clear sentence, and the free-trial note is brief. The leading 'x402-mime-type:' prefix repeats the tool name and the emoji adds noise, but overall the description is compact and front-loaded.

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 simple utility, the description is too thin. It does not explain the expected return value, which parameter to supply, or how this tool differs from closely related siblings like x402-mime and x402-mime-detect. The ambiguous optional-parameter schema makes this gap more significant.

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?

Although schema description coverage is 100%, the parameter descriptions are tautological ('Ext to process', 'Name to process', 'Filename to process', 'Extension to process') and add no real meaning. The description says 'from filename extension' but does not clarify which of the four optional parameters to use or how they relate, leaving the agent confused about whether to pass ext, extension, filename, or name.

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 states a specific verb and resource: 'Detect MIME type from filename extension.' This is clear and actionable. However, it does not differentiate this tool from sibling tools like x402-mime, x402-mime-detect, or x402-content-type, so it misses the top score.

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 such as x402-mime or x402-mime-detect. The description mentions free trial calls but does not explain the intended input scenario or any exclusions, leaving the agent without routing criteria.

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