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

The description adds substantial behavioral context beyond the readOnlyHint and openWorldHint annotations: it discloses the data source, residential proxy rendering, that only the top 4-5 options are shown, an expected ~60 s latency with a 120 s timeout, and a $0.02 USDC x402 charge only on successful calls. This is exactly the kind of operational detail an agent needs before invoking the tool.

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 front-loaded with what the tool returns and is appropriately sized for a tool with latency, pricing, and output-shape details. It is slightly dense and repeats the 'top options shown first' idea, but the content largely 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?

Given the existing output schema, annotations, and simple two-parameter input, the description is complete enough for an agent to call the tool correctly. It covers output shape, source limitations, latency expectations, and payment model.

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 required parameters documented in the input schema using examples. The description only restates that lookup is between two places, so the baseline score of 3 is appropriate.

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 states a specific resource and scope: multi-modal travel options between two places, including the headline count and top options with labels, travel time, price range, and route links. This clearly distinguishes it from single-mode siblings such as flight trackers or hotel search tools.

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 usage by saying the tool is for travel between two places, but it does not explicitly say when to use this tool versus alternatives like travel_google_travel, travel_kayak, or travel_skyscanner. There are no exclusions or alternative-selection guidance.

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