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

With no annotations provided, the description carries the full behavioral burden. It discloses two genuine traits: it returns only real data and it will offer a transfer when no direct route exists. However, it does not cover error behavior, rate limits, response structure, or how the transfer suggestion is represented, leaving notable gaps.

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 two sentences, each carrying distinct value: the first enumerates return fields, the second adds the real-data guarantee and transfer fallback. It is front-loaded, concise, and free of filler.

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 tool with no output schema and no annotations, the description lists the types of information returned and the fallback behavior, but it does not describe the response format, how transfers are structured, or how edge cases are handled. Parameter coverage is excellent in the schema, but the overall context has moderate gaps.

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 input schema already describes all three parameters fully, including accepted formats and the default date behavior. The description adds no parameter-specific meaning beyond what the schema states, so the baseline score of 3 applies.

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 lists concrete outputs—prices, number of tickets on sale, departure times, stations, carriers, and a partner purchase link—making the tool's purpose clear. It lacks an explicit verb like 'search' or 'fetch' and does not explicitly differentiate from siblings such as search_routes or find_transfer beyond the fallback mention, so it does not fully earn a 5.

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 implies this tool is for retrieving real route data between cities and notes that if no direct flights exist it will propose a connection. However, it never explicitly states when to prefer this tool over alternatives like find_transfer or search_routes, nor does it provide exclusions. Usage is therefore only implied.

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