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

Annotations already declare read-only, idempotent and open-world behavior, so the description only needs to add context — and it does: no authentication required, which carriers are covered, and the 'most Canadian carrier numbers' limitation that signals partial coverage and possible misses.

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-loaded with the core action, then progressively adds coverage, return contents, and usage trigger. The carrier enumeration is slightly long but does real work by defining supported inputs.

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?

With no output schema, the description correctly summarizes the return payload (status, delivery date, carrier scans, tracking link). It is nearly complete for a simple read tool; only the track_parcel overlap and not-found behavior are unaddressed.

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 both parameters (including the lang enum and its defaults) are already documented. The description adds no parameter-specific detail beyond the concept of a tracking number, so baseline 3 applies.

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 ('Track any parcel by its tracking number') and scopes carrier support precisely. However, it never distinguishes itself from the sibling track_parcel, which an agent choosing between the two would need.

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?

'Use this whenever someone asks where a parcel is' gives an explicit trigger condition, and 'No account needed' removes a common prerequisite question. It stops short of naming track_parcel or saying when that sibling is preferable.

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