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

Beyond the readOnly/openWorld annotations, it discloses the billing model ($0.002 USDC per successful call via x402 across Base, Solana or Arc, failures not charged), the geographic coverage boundary, and the result ordering (cheapest first) plus the pre-subsidy premium semantics. These are exactly the traits an agent needs before committing a paid call.

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 the resource and source, then coverage limits, then cost — three tight sentences with no filler. The long field enumeration earns its place by telling the agent what a record contains before it pays for the call.

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 an output schema present, the description does not need to teach return shapes, and it still covers the decision-critical gaps: cost, charging-on-failure behavior, federal-only coverage, and sort order. Nothing an agent needs in order to call this correctly 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 coverage is 100%, and every parameter already carries a schema description, so the baseline is 3. The description adds only marginal context — the age-bracket snapping to the nearest published age and the pre-subsidy premium framing — while largely restating the return fields the output schema already documents.

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 names a specific verb+resource (retrieve ACA Marketplace QHP plans for a ZIP), the upstream source (CMS QHP Landscape data), and the exact fields returned. It is unambiguous about what makes this tool distinct — federal-platform exchange plans priced before subsidies — so an agent can tell it apart from the directory-style health siblings.

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 negative constraint: federal-platform states only, states with their own exchange are not covered, which tells the agent when this tool will return nothing. It also implies the ZIP-driven use case. It stops short of naming an alternative tool for state-run exchanges, so it is not a full when/when-not/alternatives treatment.

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