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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds real value beyond them: the cost formula, the fact that gated rows are returned unranked with a reason, that advertised deals are returned separately with evidence, and that it does not enroll anyone. It stops short of describing ordering guarantees or how the annual estimate is derived beyond the formula.

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?

Front-loaded with when-to-use triggers and then behavior, and nearly every clause carries information (scope, formula, unranked rows, deal caveat). The opening is one long run-on enumeration of intents, which is dense but not wasteful.

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?

No output schema exists, so the description must carry return semantics — and it does: ranked rows by estimated annual cost, unranked gated rows with reasons, and a separate set of advertised deals with promo codes, conditions and evidence. An agent knows both what it gets and how to present it.

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 coverage is 100%, so both parameters are already documented in the schema. The description reinforces usage ('at 900 therms', 'plans of one type') and explains how therms feeds the cost formula, but adds no format or edge-case detail 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 verb (compare/rank) and resource (Georgia natural gas marketer plans) with an explicit scope: residential Atlanta Gas Light customers, ranked by estimated annual cost from PSC filings. The exhaustive 'do not use for' list (electricity, commercial, Atmos, municipal, Regulated Provider, other states, wholesale) makes it unmistakable against siblings like marketer_profile and rate_history.

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?

Front-loads concrete user intents that select this tool ('cheapest natural gas in Georgia', 'what would I pay at 900 therms', promo codes) and gives explicit exclusions with the domains it must not be used for. It also instructs how to present results relative to advertised deals rather than declaring a PSC winner outright.

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