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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds real value by disclosing the returned fields in the absence of an output schema, but it says nothing about what happens for a month with no release, whether figures are revised retroactively, or how current the newest release is.

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?

A single dense sentence with no filler; every clause maps to a distinct returned field. It is front-loaded on the resource but reads as a comma-separated field list rather than a stated purpose, which slightly costs scannability.

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 one-optional-parameter read tool with no output schema, enumerating the returned fields is exactly the compensation needed and it is present. The remaining gap is edge-case behavior for unavailable months, which is minor for a read-only index lookup.

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% and the single 'month' parameter already documents the YYYY-MM format and the omit-for-latest behavior. The description contributes no additional parameter meaning, so the baseline of 3 applies.

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 definition names the specific resource (one monthly release of the GLP-1 Cash Price Index) and enumerates its payload: cheapest verified compounded semaglutide route, cheapest branded route, the gap, median all-in price, and citation string. That is concrete enough to distinguish it from a generic price lookup, but it never explicitly contrasts with siblings like 'cheapest' or 'fair_price', leaving the boundary 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?

There is no when-to-use or when-not-to-use guidance anywhere in the description. The only usage hint in the whole definition ('Omit for the newest release') lives in the schema's parameter text, not in the description, and nothing tells the agent why it would pick this over the sibling tools.

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