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

Beyond the annotations (readOnlyHint=true, idempotentHint=true), the description discloses the paid nature ($0.03/call via x402), the payment mechanism (USDC on Base or Solana), and the 402 error behavior when unpaid. It also specifies the return shape since there is no output schema, which is valuable behavioral context.

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 and well-structured: first sentence states the core purpose, second paragraph gives usage guidance and alternatives, third paragraph covers payment and return shape. Every sentence earns its place with no filler.

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?

Despite lacking an output schema, the description provides a clear return structure, payment requirements, and tool alternatives. The five parameters are fully covered by the schema, and the usage context is complete for this tool type.

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 coverage is 100% and each parameter already has a clear description (e.g., carrier SCAC code, origin/destination UN/LOCODE filters). The tool description does not add significant parameter semantics beyond what the schema provides, so a baseline 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 opens with a specific action ('Get detailed transit schedules') and enumerates the key output dimensions (service codes, routing via transhipment ports, transit days, sailing frequency). It clearly distinguishes from the sibling tool shippingrates_transit by contrasting detailed routing versus quick transit-time comparison.

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 states when to use this tool ('when you need routing details beyond just transit time') and directs users to the alternative tool ('For a quick transit time comparison across all carriers, use shippingrates_transit instead'). This is excellent usage guidance with a named alternative.

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