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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering safety. The description adds valuable behavioral context: batch limit of 10, support for Half-Fare and GA discounts, and the requirement that trip_ids come from a recent search_connections result. This goes beyond the annotations without contradicting them.

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 three sentences long, front-loads the core purpose, and every sentence adds information. It efficiently covers scope, discounts, batching, and input provenance without redundancy.

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?

Given the simple parameter set, rich annotations (read-only, idempotent), and full schema coverage, the description is complete. It explains the price type (CHF), discount handling, batch constraints, and ID source. No output schema exists, but the description's 'Get ticket prices' clearly implies the return value, so this is sufficient.

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 covers 100% of parameters, so baseline is 3. The description adds meaning by explaining the reduction_card options ('Half-Fare card (Halbtax) and GA travelcard discounts') and by emphasizing that trip_ids must come from recent search_connections results and not be invented. This adds value over the raw schema.

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: 'Get ticket prices in CHF for one or more train connections.' It specifies the resource (train connections), the currency (CHF), and the scope (one or more). It also distinguishes itself from siblings like search_connections and get_trip_details by focusing on price retrieval and referencing trip_ids from search_connections.

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 clear usage context: 'Up to 10 trip_ids per call — batch them in a single request rather than calling once per connection' and instructs to use 'trip_ids from a recent search_connections result; do not invent IDs.' This gives practical guidance on batching and input source, though it does not explicitly mention alternatives or when not to use this tool relative to siblings.

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