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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds genuinely new behavior: it is free and consumes no quota, it caps at 10 numbers, and unregistered numbers fail softly into a `rejected` bucket rather than erroring. It does not discuss rate limits or response envelope shape, so it stops short of 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?

Dense and front-loaded: the payload contents come first, then the registration constraint, then the free/quota fact and the fallback alternatives. Nearly every clause carries weight, though the trailing 'POST /gettrackinfo' endpoint token is implementation trivia that adds nothing for an agent choosing a tool.

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?

There is no output schema, but the description compensates by enumerating the returned fields, and the annotations carry the read-only/open-world safety profile. With quota cost, batch limit, and failure semantics all stated, an agent has everything needed to call this correctly.

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 description coverage is 100% and there is a single parameter, so the schema already documents the array, the per-item carrier code, the pattern, and the maxItems=10 cap. The description restates the 10-number limit and the 'carrier needed if tracked under several carriers' nuance, which the schema also states, adding little beyond the structured fields. Baseline 3 is correct.

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 and enumerates exactly what is returned (status, sub-status, milestones, carrier events with time/location, ETA) for a bounded set of up to 10 registered numbers. It explicitly distinguishes itself from track17_register_numbers and track17_realtime_lookup, so an agent can route correctly 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 an explicit precondition (numbers must ALREADY be registered), the failure mode when it is violated (the number comes back in `rejected`), and two concrete alternatives with the condition that selects each — register first, or use realtime_lookup. This is the full when/when-not/alternative triad.

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