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

Adds substantial behavioral context beyond annotations: null/unknown handling for unpublished fields, current certified denominator (USLAX), payment requirement with 402 response, and the exact return envelope format. Highlights idempotent/read-only nature already in annotations, with no contradictions.

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?

Four sentences are front-loaded with purpose, then cover data behavior, alternative, payment, and return structure. Every sentence earns its place with no redundancy or 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?

Covers purpose, data semantics, payment constraints, alternative tool, and return envelope. Annotations provide safety profile, and description fills all remaining contextual gaps for agent invocation.

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 covers 100% of parameters with descriptions. The tool description reinforces the port parameter's USLAX denominator and gives context to x_payment, but it does not introduce new parameter-level details beyond the 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?

Description opens with a specific verb+resource+scope: 'Get certified port-authority congestion measurements for a specific port.' It clearly distinguishes from the sibling tool shippingrates_congestion_news by directing disruption advisory use there.

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?

Explicitly states when to use (certified measurements) and when not to (disruption advisories → shippingrates_congestion_news). Also discloses the paid nature and payment failure behavior, providing clear usage context.

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