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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds a genuine behavioral trait beyond that: the output is computed relative to today ('days left from today'), telling the agent the result is time-sensitive rather than a static table.

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 states scope, subject and return content with no filler. 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?

For a zero-parameter, read-only lookup with no output schema, the description gives enough to call it and anticipate the answer (deadlines plus a countdown). It could note the fixed 2027 horizon as a limitation and say whether results are year-bound, but nothing essential 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 takes zero parameters, so there is nothing for the description to disambiguate. The calendar-year scope (2027) is stated in the description, which is the only quasi-parameter context available.

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 a specific resource (the dates for changing Krankenkasse, model or deductible for 2027) and what the result contains (days left from today), so an agent knows exactly what this returns. It stops short of a verb and never references the siblings compare_insurance or draft_switch_letter, so differentiation is inferred from the topic rather than stated.

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 only implied: an agent can infer this is the tool to check switch timing before drafting a letter, but there is no explicit when-to-use statement, no prerequisites, and no mention of alternatives. The 2027 scope is the only constraint given.

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