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

With no annotations provided, the description carries the behavioral burden. It usefully discloses the x402 call price of $0.01/call, but it does not explain the calculation output format or how the split is computed, and it calls cost splitting optional even though the schema requires a 'people' parameter.

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 front-loaded and reasonably short, covering the calculation, the use case, and the call price. It contains minor awkwardness and a typo ('splitable'), plus some repetition between the calculation sentence and the 'Use this when...' sentence.

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?

The description names the main outputs (liters and total cost) and covers the key inputs, which is adequate for a simple calculator with no output schema. However, it leaves ambiguity around the required 'people' parameter and the optional-splitting claim, so an agent lacks complete guidance for 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?

The schema already documents all four parameters at 100% coverage, including units for distance, consumption, and pricePerLiter. The description adds some meaning by mentioning passenger splitting, but it explicitly calls splitting optional while 'people' is a required parameter, which can lead an agent to omit a required input.

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 and resource: calculate fuel liters and total trip cost from distance, consumption, and price per liter. It clearly distinguishes this calculator from sibling calculators such as dev_llm_cost_calculator or crypto_gas_fee_calculator by naming the fuel-cost domain.

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?

It gives an explicit use case: 'Use this when an agent needs to trip fuel and cost, splitable between people.' That is clear context, but it does not state when not to use it or name any competing alternative tool.

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