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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered without the description. The description adds real value by disclosing what content comes back, including official coverage scenarios, but says nothing about invalid/unknown plan_id behavior or the size/shape of the response.

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 front-loaded sentence that leads with the scope ('Full details for one plan') and then enumerates contents. No filler, no restatement of the title.

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 no output schema, the description carries the burden of describing return content, and it does so concretely. Minor gaps remain around error/empty handling and when to prefer check_coverage, but for a single-parameter read tool it is close to complete.

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?

Only one parameter exists and the schema documents it fully at 100% coverage (including an example id and its provenance from search_plans). The description adds no further meaning about the identifier, so the documented 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 description names the resource (one plan) and enumerates the concrete data returned: deductible, out-of-pocket max, copays, drug tiers, benefits, and coverage examples. This clearly separates it from a list/lookup sibling like search_plans, though no sibling is named explicitly.

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?

Usage is implied: fetch full detail for a single plan identified by plan_id (the schema itself points at search_plans as the source of that id). There is no explicit when-to-use vs. check_coverage guidance, which matters since check_coverage is a sibling that could plausibly overlap on cost information.

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