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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description's real contribution is data-coverage context: 2026 was the first cycle announced 2024-08, 2027 covers 15 drugs, and 2028 selections exist but prices are not yet published in the CMS file. That last point usefully warns the agent it may get no price data for 2028.

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?

One front-loaded sentence: the core action and payload come first, then the filter semantics as a parenthetical. No filler, and the parenthetical detail all earns its place by disambiguating year values.

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?

An output schema exists, so return shape need not be described; the description covers the one parameter deeply and flags the 2028 price-availability caveat, which is exactly the kind of domain nuance an agent needs for a single-optional-param read tool with annotations already carrying safety.

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 baseline is 3, but the description adds genuine meaning beyond the schema's bare '2026, 2027 or 2028. Default: all.' by explaining what each cycle is, how many drugs it covers, and whether prices are available. It does not clarify the actual return ordering or whether 2028 returns rows with null prices.

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 and resource: list the drugs CMS selected for Medicare negotiation, including Maximum Fair Prices. Scope is precise and clearly a bulk-list operation, though it never names the sibling mfp_lookup, leaving the list-vs-single-lookup distinction to inference.

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?

Usage is implied by the filter explanation — use ipay to pick a negotiation cycle — but there is no explicit when-to-use/when-not or pointer to an alternative such as mfp_lookup for single-drug detail. The cycle annotations help an agent pick a value but not choose a tool.

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