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

With no annotations provided, the description fully discloses behavior: it computes effective stored energy after efficiency losses, detects overload conditions when load exceeds watt rating, and calculates power factor. This covers key behavioral aspects, but does not detail error handling or edge cases, which keeps it from a 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?

The description is two sentences, front-loaded with the core purpose. Every sentence adds value: first sentence explains what it does and how, second provides concrete use cases. No redundant or vague phrasing.

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 tool's complexity (7 parameters, output schema exists), the description covers inputs, computations, and key features (overload detection, power factor). It is complete for a calculator tool, especially with the output schema handling return value details. The context of use cases adds completeness.

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 has 100% parameter description coverage, so baseline is 3. However, the description adds significant value by explaining how parameters are used together: 'Takes VA rating, watt rating, load in watts, and battery configuration (count, voltage, amp-hours) to compute effective stored energy after efficiency losses and runtime.' It also mentions calculating power factor, providing richer context beyond the schema.

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 it estimates UPS backup runtime from battery specifications and connected load, listing specific inputs and outputs. It distinguishes itself from sibling tools by focusing on UPS-specific calculations and mentions use cases like server rack planning and homelab power budgeting, making the purpose unmistakable.

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?

The description explicitly says when to use the tool: 'Ideal for server rack planning, homelab power budgeting, network closet UPS selection, and graceful shutdown timer configuration.' It provides clear usage context but does not explicitly state when not to use or mention alternative tools, preventing a higher score.

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