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

With no annotations, the description carries the full behavioral burden. The verb 'Get' does signal a read-only lookup and the description discloses the shape of what comes back, but it says nothing about behavior on an unknown or misspelled zone id, pagination, or any auth/rate 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 the verb first and the enumerated return fields after; there is no filler. It is efficient, though the colon-and-list construction is dense rather than maximally scannable.

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?

There is no output schema, so the description must describe the return values, and it does so concretely (per-class charge, notes, penalties, source URLs). The gap is failure behavior for an invalid zone id, which is not addressed anywhere.

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 100% and the single 'zone' parameter is documented in the schema with concrete example ids. The description adds only the loose phrase 'by id', so per the baseline rule a 3 is appropriate when the schema does the heavy lifting.

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 verb and resource ('Get one zone by id') and enumerates the returned content (daily charge per vehicle class, notes, penalties, source URLs). It implicitly contrasts with list_zones by scoping to a single zone, but never names a sibling explicitly to pin down the boundary with trip_cost.

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 lookup you call when you already know a zone id and need its charge data. There is no explicit when-to-use, no mention of when to prefer trip_cost, and no prerequisite or fallback guidance.

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