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

Annotations already declare the tool is read-only (readOnlyHint=true), and the description adds valuable context about the matching logic, such as considering stop count, direction, and backtracking, which clarifies expected behavior without redundancy. It does not introduce any contradictions and supplements the annotations with useful procedural details.

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 concise, consisting of two sentences that get straight to the point. It front-loads the primary purpose and uses the second sentence to add relevant details about the decision factors, with no fluff or repetition of schema information.

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 tool's simplicity (three parameters, no output schema), the description provides enough context for an agent to understand what the tool does and what factors are considered. It could be more explicit about the return value's format or edge cases, but for a read-only matching tool, the provided information is largely 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?

While the schema already provides descriptions for all parameters, the tool description enriches their semantics by linking 'stop count' to the cities array length, 'direction' to isOneDirection, and 'backtracking' to includeBacktracking. This additional context helps agents understand how the parameters influence the recommendation, going beyond simple type definitions.

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: recommending a fare product type for a route. It uses a specific verb ('Recommend'), names the resource ('best fare product type'), and provides concrete examples ('RTW, Circle Pacific, Circle Atlantic, Open Jaw, or Custom Multi-CCity'), distinguishing it from sibling tools like route_validate or fare_quote.

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 the tool is for matching routes to fare products by considering specific factors (stop count, direction, backtracking), but it does not explicitly state when to use this tool versus alternatives. There is no mention of when not to use it or a direct comparison to sibling tools, leaving the usage guidance implicit rather than explicit.

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