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

Annotations already declare the tool read-only and non-destructive, so the description carries a lower burden. It adds useful context by revealing the underlying endpoint (`/trains/betweenStations`) and scoping the geographic context, which supplements the structured metadata effectively.

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?

All three sentences serve a distinct purpose: what the tool does, the underlying API call, and relevant exclusions. There is no fluff or redundancy, making it a model of concise technical writing.

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 simple read-only lookup with full parameter coverage and a documented output schema, the description covers the essentials. The only minor gap is the ambiguous scope of 'when date is not provided' (i.e., what results to expect without a date), but this doesn't detract significantly from overall completeness.

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%, with both parameters ('from_station' and 'to_station') adequately described as source/destination station codes with examples. The description adds no additional parameter semantics, meeting the baseline for high schema coverage without exceeding it.

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 uses a specific verb+resource ('find trains between two station codes') that clearly states what the tool does. The qualifier 'when date is not provided' implicitly distinguishes it from the sibling searchByRouteDate, though it doesn't explicitly name the alternative.

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 both a condition for use ('when date is not provided') and explicit exclusions ('Do not use for non-India routes or booking/payment requests'). However, it stops short of naming a specific replacement tool for the excluded scenarios, keeping it at a 4 rather than 5.

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