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

No annotations are provided, so the description carries the behavioral disclosure burden. It reveals key edge-case behavior: returns null with confidence none for out-of-range prefixes, and explicitly says it does not invent a district. It could go further by describing the success response shape or behavior for malformed lengths, but the most consequential behaviors are covered.

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 purpose is front-loaded in the first sentence, and the rest of the description earns its place by explaining validation mechanics, failure behavior, and scope limitations. It is slightly repetitive about the five-digit/plate-map rule, but overall it is tight and free of filler.

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 single-parameter tool with no output schema and no annotations, the description covers the main success behavior (province resolution), the main failure mode (null with confidence none), and the scope limitation (no district). It leaves minor ambiguity about malformed input handling and exact return fields, but the overall picture is largely 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?

The input schema has 100% description coverage for the single parameter, so the schema already explains postalCode as a Turkish 5-digit code with optional spaces. The description adds useful domain context about the plate-map, but it does not add new parameter syntax or formatting details beyond the schema. Baseline 3 is appropriate.

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 opens with a specific verb and resource: 'Validates a 5-digit Turkish postal code and resolves the province from the first two digits (plate map).' It clearly distinguishes the tool's scope by stating it does not resolve districts, which separates it from broader address/validation siblings.

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 explains when to use it: for shape validation and province-level resolution. It explicitly excludes district-level resolution and notes that the full PTT directory is needed for that, giving the agent a clear boundary. It does not name a sibling tool, but the scope guidance is strong enough to route the agent correctly.

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