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

readOnlyHint=true already establishes the safe-read profile, so the description's job is to add context, which it does: it discloses the conditional nature of postage_label ('if purchased') and tells the agent what fields come back. It stops short of noting behavior for unknown ids or any rate-limit/auth characteristics.

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?

One tightly constructed sentence front-loads the action and resource, then adds the notable return fields and the underlying endpoint with no filler. Nothing is padded or redundant.

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 one required parameter, full schema coverage, and no output schema, the description carries the return-value burden and does so by naming the key fields. It is essentially complete, missing only error/not-found behavior for an invalid id.

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?

There is a single parameter with 100% schema description coverage, so the baseline is 3. The description restates the id-based lookup but adds no format, prefix, or lookup guidance beyond the schema's own 'shp_...' example.

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 (Retrieve), a precise resource (a single shipment by id), and enumerates the meaningful payload (rates, tracking_code, postage_label). This clearly separates it from easypost_list_shipments and the write siblings such as buy_shipment or refund_shipment.

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 is implied by 'by id' and the sibling set — fetch a known shipment id after creation — but there is no explicit when-to-use statement, no pointer to list_shipments for discovering ids, and no stated condition for when not to call it.

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