percentage_change_calc

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

With no annotations, the description must carry the behavioral transparency burden. It does disclose that the tool costs $0.001 USDC via x402, which is a useful constraint. However, it fails to mention whether the tool is synchronous, what the return format is, or any side effects beyond cost.

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 short and avoids wordiness, but it is under-specified. It reads more like a label than a functional description, making it too sparse to earn a higher score for structure.

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?

This tool has no output schema, no detailed input schema, and no annotations. The description provides only a category and a cost note, leaving the agent without essential information about what the tool computes, how to invoke it, or what results to expect. It is incomplete even for a simple calculator tool.

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?

The input schema is a generic 'params' object with no actual parameter definitions. Although schema coverage is 100%, the description for 'params' ('Tool parameters as JSON object') provides no meaningful semantics. The description also does not explain what parameters should be passed (e.g., old value and new value), so the agent has no idea how to construct a valid request.

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 essentially restates the tool name ('percentage change calc') with a broad category label ('Finance & Math tool'). It does not explicitly state what the tool does, such as 'calculates the percent change between two values.' While the name hints at the purpose, the description itself lacks a clear verb+resource statement.

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?

No guidance is provided on when to use this tool versus alternatives. There are many sibling tools, including percentage_calculator and various financial calculators, but the description does not differentiate this tool or offer any selection criteria.

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