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

No annotations are provided, so the description must carry the full burden. It does not specify whether masking is reversible, what format the output takes, or which parts of the phone number are preserved. 'Mask' implies redaction, but the depth of masking and its applicability (e.g., partial vs full) are unspecified.

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 description is extremely short and lacks substance. While concise, it fails to front-load any useful information and provides no structure to guide an agent beyond the name.

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?

Given the absence of annotations, output schema, and rich parameter descriptions, the description is insufficient to help an agent invoke the tool correctly. It should clarify the masking behavior, expected input formats (e.g., phone number string), and any limitations.

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 100%, with both parameters ('text' and 'input') documented as 'Text to process' and 'Input to process'. However, these descriptions are generic and do not clarify their distinct roles for phone masking. The baseline score of 3 is appropriate given the full schema coverage, but the description adds no extra meaning.

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 'Mask Phone: Mask phone.' is a tautology that merely restates the tool name. While 'mask phone' implies redacting phone numbers, the description provides no additional clarification of scope or behavior beyond the name itself.

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 or why to use this tool versus alternatives. With many related tools like x402-mask, x402-mask-email, x402-mask-card, and x402-validate-phone in the sibling list, the lack of context switching guidance is a notable gap.

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