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

Annotations already declare readOnlyHint=true, and the description reinforces this ("Sola lettura"). It goes further than annotations by naming the returned fields (subject, sender, date, excerpt) and, importantly, warning that emails are third-party untrusted data that must never be treated as instructions – a genuinely valuable safety disclosure. It omits auth/pagination details, so not a full 5.

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?

Three tight sentences: resource and content scope first, then the mode logic, then the safety caveat. Zero filler and the most decision-relevant information is front-loaded.

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 read-only, two-parameter tool with no output schema and annotation-covered safety, the description covers both modes, the return fields, and a prompt-injection warning – enough to call it correctly. The only real gap is the undocumented «limite» parameter.

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?

Schema description coverage is 0%, so the description must carry the parameter burden. It explains «id» well (presence selects single-email read), but «limite» (1-50, the list cap) is never mentioned in either the schema or the description, leaving half the parameters unexplained. Partial compensation warrants a 3.

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 and resource (reads the city's inbox at a named address), enumerates the content types (newsletter, subscription confirmations, notices), and spells out the two operational modes driven by the «id» parameter. An agent can distinguish this from siblings like leggi_documento or leggi_registro without opening any schema.

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 clearly conditions behavior on «id» (absent = list recent mail, present = read one), which is useful operational guidance. However it never states when to prefer this tool over alternatives such as cerca_archivio, nor any prerequisites or exclusions, so routing between siblings is left to inference.

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