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

Beyond the readOnly and openWorld annotations, it discloses genuinely non-obvious behavior: multiple candidates may match the same pattern, each candidate reports whether its check digit passed, and check digits are only checked where the carrier publishes one. It also states the payment model (x402 at $0.002 USDC per successful call, failed calls free) — auth/pricing context the annotations do not carry.

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 purpose, followed by candidate semantics, the negative scope, and pricing. Every sentence is informative, though the payment sentence is long and packs three chain names where two would do.

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 an output schema present and annotations covering read-only/open-world, the description supplies everything an agent needs: input format, multi-candidate behavior, check-digit semantics, exclusion of live scans, and the paid-call mechanics.

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 schema coverage is 100% and the single parameter already documents that spaces are allowed. The description only adds that matching is format-based, which is marginal beyond the schema, so the baseline of 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: identify the carrier behind a tracking number from its format, verify check digits, and return the official tracking link. It also carves out scope against tracking siblings by declaring it does not read live scan events, which distinguishes it from container/UPN tracking tools.

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?

The when-to-use context is clear (you have a tracking number and need the carrier and official link), and there is an explicit exclusion: no live scan events. It stops short of naming the sibling tools an agent should pick instead for container or postal-UPN lookups, so it is strong but not fully routing.

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