Calculate percentage change between two values.
| Name | Required | Description | Default |
|---|---|---|---|
| new_value | Yes | New value | |
| old_value | Yes | Original value |
| Name | Required | Description | Default |
|---|---|---|---|
| code | No | ||
| error | No | ||
| direction | No | ||
| new_value | No | ||
| old_value | No | ||
| percent_change | No | ||
| absolute_change | No |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations exist, and the description does not disclose behavior for edge cases (e.g., division by zero if old_value is 0) or the return format (e.g., whether result is 50 for 50% or 0.5).
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?
Extremely concise single sentence, front-loaded with essential information, no wasted words.
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?
Despite simple parameters and presence of output schema, the lack of behavioral transparency and usage guidelines leaves gaps for an AI agent, especially among numerous sibling tools.
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 descriptions are trivial ('New value', 'Original value'), and the tool description adds no extra meaning. High schema coverage (100%) sets baseline at 3.
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 clearly states the action 'Calculate' and the specific resource 'percentage change between two values', distinguishing it from sibling tools like 'percentage' or 'calculate_margin'.
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 provided on when to use this tool versus alternatives (e.g., 'percentage' or 'calculate_discount'). No mention of appropriate contexts or exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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