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

Annotations declare the safety profile (readOnlyHint=false, destructiveHint=true, idempotentHint=false), and the description adds substantial context beyond that: quota consumption per accepted number, zero cost for rejects, cost on delete-and-re-register, automatic carrier detection, 6-12h self-refresh, disabled e-mail notifications, and the POST endpoint.

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?

Front-loads the critical 'WRITE (uses quota)' marker, then packs only decision-relevant facts into tightly constructed sentences with no filler; every clause earns its place.

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 mutation tool with no output schema, the description covers cost, quota, carrier resolution, refresh cadence, and the read path, so an agent has nearly everything needed. It could say a bit more about the per-number response shape (e.g., what a rejection looks like), but the gaps are minor.

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%, so the baseline is 3, but the description adds real meaning beyond the schema by stating the carrier is auto-detected unless a carrier code is supplied and by tying the array to the 10-number cap. This clarifies behavior of the carrier field that the schema only enumerates.

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+resource ('start tracking up to 10 tracking numbers per call') and is immediately distinguishable from siblings by naming track17_get_tracking and track17_get_quota. An agent knows exactly what this does 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?

Clearly routes the agent: check costs via track17_get_quota and read status via track17_get_tracking, and explains the cost economy of accepted vs rejected numbers. It stops short of explicitly contrasting with track17_retrack (re-registration) or track17_realtime_lookup, so it is clear context but not 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.