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

Annotations already declare readOnlyHint and openWorldHint, but the description adds substantive behavior: data provenance (CMS monthly formulary files), freshness (includes CMS release date), year scope, and a pay-per-call price with failed calls not charged. The payment model is critical context an agent would otherwise miss; it lacks only detail on latency or result size.

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-loads what the tool is and what it returns, with pricing correctly appended last. The long field enumeration is dense but each item earns its place; the description is a single run-on sentence plus a payment sentence with little 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?

For a read-only open-world lookup with an output schema (returns needn't be explained), the description covers source, year scope, query modes, key outputs, freshness, and payment terms. Nothing an agent needs to call it 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%, so the schema already documents all five parameters. The description adds meaning by showing how 'plan', 'state', and 'limit' correspond to the different query modes and by clarifying year scope, but does not go beyond what the schema describes for individual parameters.

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 (lookup), resource (Medicare Part D formulary coverage), and enumerated outputs (tier, PA, step therapy, quantity limit, cost share, premiums). The field list makes it unmistakable versus generic siblings like health_cms_medicare_part_d or health_rxnorm_concept_id.

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?

Clearly frames the three query modes (one plan via 'plan', state listing via 'state', or every formulary) and notes year coverage (current and next plan year), giving the agent a scaffold for choosing parameters. It stops short of naming alternatives or when-not-to-use cases.

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