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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, but the description adds material facts an agent cannot get from them: a 10-item per-call cap, a lifetime limit of 5 carrier changes per number, the billing consequence ('charged as one shipment'), and the underlying POST /changecarrier endpoint. Error/partial-failure behavior and retry semantics against the 5-change budget remain undisclosed.

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?

A single dense sentence, front-loaded with the operation class ('WRITE:'), then capability, limits, cost, and endpoint in descending order of importance. 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?

For a destructive, billable mutation with strong annotation coverage and no output schema, the description supplies the limits, cost, quota cross-reference, and transport detail an agent needs. It stops short of describing failure modes (e.g., what happens when the 5-change limit is exceeded or a number isn't registered) and any auth/prerequisite context.

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 description restates the per-call cap ('up to 10') that is already enforced by the schema's maxItems, so it adds little parameter-level meaning. It says nothing about what carrier codes are valid (carrier_new is an unenumerated integer) or when carrier_old is required beyond what the nested schema descriptions already state. With the reported 0% schema description coverage, more compensation was expected.

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 ('assign a different carrier to registered tracking numbers') and leads with a 'WRITE:' marker that instantly separates it from read siblings like track17_get_tracking or track17_realtime_lookup. The 'for example when auto-detection picked the wrong one' clause clarifies the scope of the operation. An agent can distinguish this from track17_change_tag without opening either 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 a concrete trigger scenario ('when auto-detection picked the wrong one') and routes cost-checking to the sibling track17_get_quota. It does not state when NOT to use it (e.g., before registering numbers, or instead of track17_register_numbers), so it is clear context rather than full when/when-not guidance.

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