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

With no annotations, the description carries the full burden. It discloses the return content (list of municipalities plus ISTAT codes), which is useful given there is no output schema, but says nothing about read-only safety, whether a single ZIP can map to multiple municipalities, or any auth/rate-limit constraints.

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 with no filler. The verb and resource lead, and the keying field is stated last without redundancy.

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 simple one-parameter lookup with no annotations or output schema, the description covers the core operation. However, it omits input format guidance and the possibility of multiple results per ZIP, which are the main things an agent would still need.

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?

There is one parameter and schema description coverage is 0%, so the description must compensate but only implies that zip_code means an Italian ZIP. It gives no format, length, or example (e.g., 5-digit CAP), leaving the agent to guess the accepted input syntax.

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 (retrieves), resource (Italian municipalities and their ISTAT code), and lookup key (ZIP code). The 'by_zip' framing implicitly differentiates it from siblings like find_IT_municipality_by_istat and find_IT_istat_by_comune_name, though it never names them 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 only implied by the lookup direction: you use this when you have a ZIP code and want the associated municipalities. There is no statement of when to choose this over the ISTAT- or comune-name-based siblings, and no exclusions or prerequisites are given.

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