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

Annotations already declare this read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new context: that the content is an authoritative, year-stamped (2026) reference with cited official sources, and that it explicitly documents what is NOT modelled — which tells the agent what confidence to place in answers. It does not say whether the content is static or refreshed, but that is a minor gap.

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 sentences, no filler: the content inventory comes first, the call-to-action second. Both sentences earn their place. Minor wording like "the options they take" is slightly oblique about what an "option" is, but it does not cost much.

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 reference tool with no output schema, the description needs to preview what comes back, and it does — rules, options, unmodelled areas, sources. Combined with annotations that establish safety and closure, an agent has enough to know when and how to call it; only the format/length of the response is left unstated.

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 no parameter semantics to explain and the baseline of 4 applies. The description correctly implies a no-argument, informational lookup rather than a configurable query.

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 definition states concretely what the tool returns: the Turkish tax rules the calculators implement for 2026, the options accepted, the gaps in modelling, and the official sources. That content list separates it from the sibling calculators (net_salary, employer_cost, compare_with_netherlands), which compute rather than document. It is a noun-phrase inventory rather than a verb+resource statement, which keeps it short of a 5.

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?

"Call it before answering a question the other tools may not cover" gives a clear positive trigger, positioning it as a coverage/fallback check ahead of the calculation tools. It stops short of naming which sibling to try first or stating when-not to bother, so there is no explicit exclusion.

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