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

Annotations already declare read-only, idempotent, non-destructive behavior, so the bar is lower; the description still adds real scope information by disclosing the at-least-one-parameter constraint and the 'current rate only / no historical' limitation. It does not describe response shape or multi-match behavior when utility is partial.

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?

Three sentences, each earning its place: definition first, input constraint second, scope limitation third. No filler and nothing buried.

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?

With no output schema, the description does some work by saying only the current rate is returned, and it covers the input requirement. It leaves open what comes back if utility matches multiple entries or if both state and utility are supplied, which is a modest gap for a lookup tool.

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 baseline is 3, but the description adds meaning beyond the schema: the schema lists no required parameters (required: 0), while the description correctly states at least one of state/utility must be supplied. That is genuine additive semantics, though the partial-match behavior of utility is already covered by 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?

States a specific resource — the current utility price-to-compare (PTC) / default-service rate — and even defines what the benchmark means, so an agent knows exactly what it retrieves. It does not differentiate itself from siblings get_utility_by_zip or search_plans, which keeps it short of a 5.

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?

Explicitly states the input requirement ('supply state, utility, or both; at least one is required') and an exclusion ('historical PTC is not available... must not be inferred'). It stops short of naming the alternative sibling tools to use instead, so it is clear context without explicit routing.

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