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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds the scoping constraint (one letter of the A-Z directory) and the fact that results carry slugs, but says nothing about pagination, result volume per letter, or rate limits. Similar to the calibration case, this is useful but not rich behavioral context.

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?

Two sentences, zero filler, and the scoping constraint plus the slug payload are front-loaded before the routing advice. Every clause earns its place.

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, return values need not be explained; annotations cover safety and openness; the single parameter is documented. The description adds the bridge-to-goodrx_drug_prices workflow, leaving nothing an agent needs to call this correctly.

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 letter parameter is fully documented in the schema, including the enum-like list of values. The description restates 'one letter (a-z)' without adding format or syntax beyond the schema, so the baseline 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?

States a specific verb (list) and resource (every drug in one letter of GoodRx's A-Z directory) and adds the distinguishing output detail that entries carry price-page slugs. An agent can separate this from goodrx_drug_prices without opening either schema.

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?

Explicitly names the condition ('when you only know a drug's name') and routes to the alternative tool (goodrx_drug_prices) that consumes the slug. This is a textbook when-to-use statement with the sibling named.

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