Fare options for one journey

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is known. The description adds useful behavioral context: fares are 're-checked live' and are informational only, not a booking. This goes beyond the structured annotation data without contradicting it.

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?

Three purposeful sentences: scope and fare types first, usage trigger second, informational caveat third. No filler, and every sentence earns its place.

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 5-parameter tool with an output schema and safety annotations, the description is largely complete: it identifies the required recon_token, explains sequencing, and sets expectations about live pricing and non-booking. The only notable gap is that it does not explicitly distinguish itself from db_best_price, but the wording 'all fares' vs 'best price' mostly covers that.

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 only 40%; only recon_token and bahncard get explicit descriptions. The description reinforces that recon_token comes from a db_journeys result and mentions 'class', which loosely maps to first_class, but it does not compensate for the undocumented adults, first_class, and children_ages parameters. Parameter semantics remain mostly left to inference.

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 names a specific verb and resource: it returns all fares for ONE specific connection, with concrete fare types (Super Sparpreis, Sparpreis, Flexpreis, regional day tickets) and includes price and class. This distinguishes it from journey search and from a best-price-only tool.

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 explicitly says to use it after db_journeys when the user asks 'how much' or 'cheapest ticket', which gives clear invocation context. It also states prices are informational and not a booking, but it does not explicitly name or exclude the alternative db_best_price.

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