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

Annotations already declare readOnlyHint=true and openWorldHint=true, but the description adds a crucial non-obvious trait: 'It spends a metered upstream call.' This is beyond the annotations and informs the agent about cost/rate limits, influencing call frequency. It also states 'Live' availability, aligning with openWorldHint. No contradictions with annotations are present.

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 with no waste. It front-loads the core function, then adds the alternative-bookings detail and a practical warning about the metered call. Every sentence earns its place, making it concise and well-structured.

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?

With no output schema, the description should clarify what the tool returns. It mentions 'seat availability per class' and alternative booking options but doesn't describe the response structure, such as how alternatives are listed or whether quotas are included. While the purpose is clear, an agent may not know exactly what to expect from the output, making it incomplete.

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 coverage is 50%, with descriptions for 'from', 'to', and 'include_rac' but not for 'train_number', 'date', or 'quota'. The description refers to 'one train on one date' implicitly covering train_number and date, and 'per class' implicitly relating to quota, but it doesn't explain these parameters explicitly. It partially compensates for missing schema details but leaves room for ambiguity, especially regarding 'quota' and date format.

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 function: 'Live seat availability per class for one train on one date' and further specifies it covers alternative booking methods when the through ticket fails. It distinguishes itself from sibling tools like train_schedule or journey_calendar by focusing on booking options and waitlist rescue, with the phrase 'This is the tool that rescues a waitlisted train.' This makes the purpose specific and distinguishable.

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 gives clear context for when to use it: 'when the through ticket will not confirm' and 'rescues a waitlisted train.' It also advises to query only trains the traveller is actually considering, which is a practical usage guideline. While it doesn't explicitly name alternatives to avoid, the unique use case is well defined, making the intended scenario obvious.

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