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

Annotations already declare readOnlyHint and idempotentHint, and the description does not contradict them. It adds useful behavioral context by specifying what the returned list contains (medicines, lowest published monthly price, and provider count), which is especially valuable given there is no output schema.

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?

The description is a single well-structured sentence with no filler. It front-loads the primary action and resource, then efficiently adds the key output details and examples of included medicines in parentheses.

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 zero-parameter, read-only list tool, the description is largely complete: it names the medicines, the comparison context, and the returned data points. It could slightly improve by noting currency or sorting, but given the tool's simplicity, 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?

The tool has zero parameters and the schema description coverage is 100%, so there are no parameter semantics to clarify. The description's mention of the output fields is the only relevant semantic information, and it provides sufficient clarity.

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 description states a specific verb ('List'), a clear resource ('UK weight-loss medicines compared on WeightMedsCompare'), and the exact output fields (lowest published monthly price and number of providers). This clearly differentiates it from sibling tools like get_provider or search_providers, which focus on individual providers rather than the medicine list.

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?

The description implies when to use the tool: when the agent needs an overview of all compared weight-loss medicines with prices and provider counts. However, it does not explicitly state when not to use it or how it compares to the sibling tools, leaving the routing decision to inference.

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