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

Annotations already declare readOnly, idempotent, closed-world, non-destructive, so safety needs no restating. The description adds genuinely new behavior: there is no paging and the full list is always returned, plus a sketch of the return shape, which matters since no output schema exists.

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 short sentences, front-loaded with what the tool returns and followed by the use cases, with labeled 'Optional:' and 'Returns:' clauses. Minor waste in repeating the live_only default already in the schema.

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 one-parameter read tool with no output schema, the description covers purpose, call sites, pagination behavior, and a return-value sketch. Nothing an agent needs in order to call it correctly is missing.

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 coverage is 100% and the single `live_only` parameter already carries a description and default of false, so the description's restatement ('Optional: live_only (default false)') adds little. The Returns sketch is useful but belongs to output rather than parameter semantics.

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?

States a specific verb and resource (list the carriers BerthTime knows) and immediately enumerates the payload fields: SCAC, name, ref_types, tracking. No sibling tool overlaps with carrier enumeration, so an agent can route here without opening the schema.

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?

Gives two concrete usage contexts: resolving the SCAC needed for track_shipment's `carrier` argument, and answering 'do you support X'. It stops short of explicit when-not guidance or naming an alternative (there is no sibling carrier tool), so it lands just under the top score.

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