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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavior: results carry mode and status, and the 'accepting' status is a gate for downstream estimation, which an agent would otherwise not know. Return shape details beyond those two fields are absent, keeping it below a 5.

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?

Two short sentences, no filler, with what the tool returns stated first and the status constraint second. Every clause carries information an agent needs.

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?

For a zero-parameter, read-only enumeration with no output schema, the description covers the essentials: the resource, two returned fields, and the status rule that affects downstream calls. It stops short of describing the full record shape or ordering, but the gaps are minor at this complexity.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline of 4 applies. Nothing in the description mischaracterizes the parameterless contract.

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 names the resource concretely as "shipping routes (lanes)" and clarifies the domain synonym, then states the attributes returned (mode, status). It is clear what the tool returns without opening the schema, though it does not explicitly contrast itself with any sibling such as estimate_delivered_cost.

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 second sentence implies usage by stating that only lanes with status 'accepting' can be estimated, which hints this is a discovery step before estimation. However, it never says when to call this tool versus alternatives nor names the estimation tool it gates, so the guidance remains inferential rather than explicit.

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