List every drug in one letter (a-z) of GoodRx's A-Z directory with price-page slugs. Use to find the slug for goodrx_drug_prices when you only know a drug's name.
| Name | Required | Description | Default |
|---|---|---|---|
| letter | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes | The tool result payload (shape varies per tool; see each tool's docs resource). |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=true, so the read-only, open-world nature is covered. The description adds that results carry price-page slugs, which is meaningful payload context for the downstream call, though it says nothing about pagination 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?
Two tight sentences with no filler: the first describes what is returned, the second the when-to-use and the alternative. Front-loaded with the scoping constraint.
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-parameter enumeration tool with an output schema, the description supplies purpose, parameter constraint, and routing guidance. Return structure is handled by the output schema, so nothing critical 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 0%, so the description carries the burden for the single 'letter' parameter. It specifies 'one letter (a-z)', constraining cardinality and domain, which is more than the bare schema provides, though it doesn't state case sensitivity or behavior for invalid input.
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) plus the payload attribute (price-page slugs). An agent can distinguish this from siblings like goodrx_drug_info or goodrx_drug_prices without opening the 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 alternative (goodrx_drug_prices) and the condition that selects it (when you only know a drug's name), which is exactly the routing guidance an agent needs for a lookup chain.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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