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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond that: it discloses that the tool 'Costs 1 call' and returns plan counts with as_of dates. It does not discuss pagination or response size, but the output schema exists and likely covers return shape.

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 short, front-loaded with what the tool returns, followed by filtering and usage guidance, and ends with a useful cost note. Every sentence earns its place with no wasted text.

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 rich annotations, full schema coverage, and presence of an output schema, the description provides everything an agent needs: purpose, filters, usage context, and cost. No critical behavioral or parameter detail is missing.

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 the schema already fully documents the year, state, and market parameters, including defaults and enum meanings. The description merely restates that filtering is possible without adding syntax, format, or default details beyond the schema. Baseline 3 is appropriate.

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 the resource: markets, states, and insurers with directory listings, plus plan counts and as_of dates by plan year. It also explains the intended use (seeing which states and insurers are queryable), which implicitly distinguishes it from plan/provider lookup siblings. However, it does not explicitly name or contrast with any sibling tool, so it falls 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?

It gives a clear usage statement: 'Use it to see which states and insurers you can query,' and notes the available filters. There are no explicit when-not-to-use conditions or named alternatives, but the context is sufficient for an agent to know when this metadata/coverage tool is appropriate.

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