Find percent-of values, determine what percent one number is of another, and compute percentage increase, decrease, or change.
Calculate percent-of, what-percent, increase/decrease, and percentage change.
| Name | Required | Description | Default |
|---|---|---|---|
| x | Yes | ||
| y | Yes | ||
| operation | Yes |
Changes observed during successful MCP inspections.
v0.2.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden but discloses almost nothing about behavior: it doesn't state whether the tool is pure, deterministic, how it handles errors or edge cases, or what the return format is. It merely enumerates operation names.
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 a single, front-loaded sentence with no redundant or filler content. It is appropriately sized for a simple calculator tool.
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 3 required parameters, no annotations, no output schema, and 0% schema description coverage, the description is too sparse. It should clarify parameter roles and provide at least minimal usage context to ensure 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%, so the description must compensate. It lists operation types that map to the enum, but it does not explain the roles of x and y for each operation (e.g., which is the percentage and which is the base for percent_of). This leaves parameter semantics largely ambiguous.
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 (calculate) and resource (percentage) and lists several operation modes, which helps distinguish it from generic math tools like calculate_expression. However, it does not explicitly differentiate itself from siblings or clarify its scope relative to them.
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 such as calculate_expression or calculate_finance. There are no prerequisites, exclusions, or context for selecting among the listed operations.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.