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

With no annotations, the description carries the burden and does well: it discloses the data source (hand-written catalogue of 110 cities), that unknown cities produce an error rather than an estimate, and that figures are never interpolated. It does not describe the error payload or the exact response shape, which keeps it short of a 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?

Two sentences, front-loaded with what the tool returns, followed by the provenance and failure constraint. No filler or restatement of the title.

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 one-parameter, no-output-schema tool, the description covers return structure, data provenance, and failure behavior. The only gap is that an agent is not told the error format or how to recover when a city is missing.

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 schema fully documents the single city parameter, so the baseline is 3. The description adds real meaning by constraining valid values to the 110-city catalogue, warning the agent that approximate or unlisted city names will fail rather than resolve.

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 states a specific resource (daily cost in a city) with an explicit dimensional breakdown (budget/mid-range/luxury × accommodation, food, transport, activities) plus editorial overview. It is clearly a single-city cost lookup, distinct from compare_destinations and find_destinations.

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 tool for per-city cost detail, but the description never names compare_destinations or find_destinations or states when to prefer them. The catalogue-membership note is a constraint, not routing guidance.

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