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

Annotations declare readOnlyHint=false and destructiveHint=false, so the write-but-non-destructive profile is already covered. The description adds genuinely useful context in 'No charge' (billing behavior) and the return of current status, but says nothing about idempotency or what happens if a tracker for the same code already exists.

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 short, front-loaded sentences with no padding; the purpose and cost note come first. The trailing 'API: POST /trackers (body { tracker })' is marginally useful but leans on internal API jargon that adds little for tool selection.

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 compensates by stating that it returns the tracker with current status. Nothing critical is missing for a simple two-param creation call, though duplicate-handling behavior would round it out.

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%, so both parameters (carrier, tracking_code) are already documented including the carrier disambiguation hint. The description only restates that it works via carrier tracking code, adding no syntax or format detail beyond the schema — 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+resource ('Start tracking a package by its carrier tracking code') and clarifies the operation creates a tracker rather than fetching one. However, it never names the obvious sibling easypost_get_tracker, so the agent must infer the create-vs-retrieve distinction from the name alone.

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?

Implies usage (you have a tracking code and want to begin tracking), and 'No charge' hints this is a safe/cheap call. But there is no explicit when-to-use guidance or contrast against easypost_get_tracker / easypost_list_trackers.

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