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

Annotations only cover read-only and open-world characteristics, but the description adds a genuinely important behavior not in structured data: a $0.002 USDC per-call charge under x402. It also describes the return arrangement (ranked cheapest first, 12-month change, US average), which no output schema supplies. Rate limits and failure modes remain undisclosed.

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?

A single dense sentence that front-loads the resource and coverage, with cost last. Nothing is wasted, though the parenthetical sector list and the cost clause make it slightly congested for one 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?

For a two-parameter read-only tool with no output schema, the description covers coverage, units, sorting, comparative fields and the billing requirement. It is near-complete; only tiered/error behavior and how the free vs paid boundary works are unaddressed.

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 100%, so both parameters are already documented in the schema; the description only echoes the sector vocabulary and the 'every US state' scope. It adds no syntax, default or filtering nuance beyond the schema, so the baseline of 3 applies.

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?

States a specific resource (electricity prices), scope (every US state, latest month), granularity options (residential/commercial/industrial/all), unit (cents per kWh) and ordering (cheapest first). It is easily distinguished from the adjacent energy_gas_prices and energy_mix siblings, which cover different resources.

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 implies when the tool is useful (state-level retail electricity rate comparison for the latest month) but names no alternatives or exclusions, so an agent must infer whether to pick this over energy_gas_prices, energy_mix or energy_forecast from names alone.

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