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

Beyond annotations (readOnlyHint, openWorldHint), the description discloses key behaviors: synchronous execution, immediate full results, no tracker creation, per-call billing, and subscription dependency. This is exactly the kind of contextual behavior an agent needs and exceeds what annotations alone provide. No contradiction with annotations.

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?

Three tightly packed sentences: first defines purpose and typical use, second states behavioral outcome and billing model, third provides fallback. No filler; each sentence adds distinct value and the key differentiator is front-loaded.

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?

The output schema is present, so return details need not be spelled out. The description covers when to use, how it behaves, what side effects it avoids, cost implications, and what to do on failure. For a six-parameter tool, this is complete and actionable.

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%, with detailed parameter descriptions including format, constraints, and courier-specific validation notes. The tool description does not add parameter-level meaning, but the schema already handles it, so baseline 3 is appropriate.

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?

The description states a specific verb and resource: one-off tracking lookups with natural-language examples ('track X', 'where is my package'). It explicitly differentiates from siblings by labeling itself 'Default tool' and clarifying it is a synchronous per-call endpoint that creates no tracker, making its role distinct from track and create_tracker.

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?

Usage guidance is explicit: it is the default for one-off lookups, and it provides a concrete routing rule for failure — if no_active_subscription occurs, use track instead. This gives an agent a clear decision boundary between search_tracking and its alternatives.

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