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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a non-mutating, externally-sourced lookup. The description adds genuinely useful behavior context — that plan durations vary per medication and must be discovered first — but does not explain error behavior for invalid medication/form/duration combinations or whether prices are live/volatile.

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?

Three front-loaded sentences: purpose, return content, then the critical prerequisite. The return-breakdown sentence is slightly redundant since an output schema exists, but it is short and the sequencing warning is correctly emphasized.

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 annotations covering safety and an output schema covering return shape, the description supplies the remaining decision-relevant facts: required inputs, the dependency on medications_details, and the supported catalog. Only failure modes and price freshness are left unaddressed.

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 would be 3; the description earns a point by explaining that plan_months is not a free choice (values vary by medication) and by listing supported medication names. Slight tension remains: the schema advertises (1, 4, 6) while the description says durations vary, which an agent must resolve by calling medications_details.

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+resource ('Get detailed pricing') and pins the three dimensions that define the request (medication, form, plan duration). It also names the sibling it depends on (medications_details) and enumerates supported medications, so an agent can separate it from medications_availability and medications_list 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 states a prerequisite sequence: 'use medications_details first to see available plan_months values,' which prevents a failed call with an invalid duration. It does not state when-not to use this tool (e.g., versus medications_availability), so it stops short of a full routing rule.

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