plan_trip

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

With no annotations, the description must carry the full burden. It discloses the core comparison behavior and the fact that it returns a cheaper option, but does not elaborate on output format, data sources, assumptions, or limitations. This is adequate but not rich.

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 description is extremely concise: two sentences that front-load the core purpose and then provide a direct usage guideline. Every sentence adds value, with no redundant or fluffy content.

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?

The tool is relatively simple: three parameters, no output schema, no annotations. The description covers the tool's purpose, its comparison logic, and when to use it, which is sufficient for a basic understanding. It lacks detail on return value structure but does mention 'says which is cheaper,' offering minimal output guidance. This is complete enough given the tool's moderate complexity.

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 provides 100% coverage with detailed descriptions for all three parameters, so the baseline is 3. The description does not add significant parameter-level meaning beyond what the schema already states; it merely references the multi-country aspect. Therefore, a 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 clearly states the tool's purpose with a specific verb ('work out') and resource ('the cheapest way to stay connected across several countries'). It distinguishes itself from siblings by focusing on multi-country trip cost comparison, contrasting a single regional plan versus per-country local plans, and explicitly says it outputs which is cheaper.

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 provides a clear usage condition: 'Use this whenever the user names more than one destination.' This gives explicit when-to-use guidance. However, it does not explicitly mention when NOT to use or name alternative tools for single-destination scenarios, so it falls short of a 5.

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